Lý thuyết tăng trưởng PGS TS đàm xuân hiệp

PGS. TS. DAM XUAN HIEP
Lt rrnuykr
TANG TRIJONG
iii
NHA XUAT BAN KHOA HOC VA 1(1
7
THU lAT
HA NOI
- 2010
Lol N61 Mill
Tang tru6ng luOn la chii de ciia nhieu cuOc tranh luan khac nhau gida
nhieu nha kinh to hoc, giira nhieu tm6ng phai hoc thuyet khac nhau. DO
cling la van de dapc nhieu nha nghien cdu cling nhu thkrc hanh chinh sach
vi me quan tam.
Tim du'oc ban chat citing clan cna tang truCing co the gitip Ich cho cac
nha hoach dinh va ra guy& dinh chInh sach kinh to cua mot qu6c gia.
Cu6n sach nay dua ra mot gOc nhin
ye
ban chat dm tang tru6ng.
Thoat dau, cuon sach dupe bien soar' nham phuc vu mot phan cho cac bai
giang trong mOn chuyen de to chpn "1/ thuyet kinh to dOng" ma tac gia
thtic hien tai mot so khod cao hoc nganh Quan tri Kinh doanh cua truerng
Dai hoc Bach Khoa Ha NOi. Tuy nhien, tai lieu cling co the duorc dimg de
phuc vu hoc tap cho sinh vien va cac can 1D0 nghien cau cua cac chuyen
nganh khac lien quan den kinh to hoc vi mo nhu: kinh to cOng nghiep, kinh
to nang lacing._ CuOn sach bao g6m nhang not dung co ban nhu sau:
Chuang I: Tang trua'ng can bang.
Chuang 2: Nguyen ttic yang caa tang trtang vci van
de'
phan chic
thu nhap.

Chuang 3: Phdn tich them ve ccich nhin tan co
Chuang 4: Tang tniong phi can bang.
Chuang 5: Tang truang nOi sinh va tang truang ngoai sinh.
Chuang 6: Cac mo hitzh phi can bang.
Chuang 7: Ccic !no hinh can bang.
3
Day la Ian xuat ban dau tien nen có the cuein sach khOng tranh dugc
thieu sot
v6
not dung lan hInh thdc trInh bay. Chung tOi rat mong nhan
dtroc cac y kien &rig gop cUa dpc gia de nang cao chat luong cu6n sach
trong Lan tai ban tiep theo. Noi tie'p nhan cac
Y
kien: Nha xuat ban Khoa
hoc va Ky thuat - 70 Tran Hung Dao - Ha NQi; hoac dia chi email:
hiepdx(&epu.edu.vn
.

Tran trong cam on!
Tdc gid
TANG TRUING CAN BANG
Trong thuyet
"can bdng tang guar
cUa Keynes, Ong da gia thiet
rang lacing dkr trfr tu ban khOng d6i va dpc lap vOi dau to trong 14. Trong
mO hinh
"khd Wang tang tradng can bdng",
Keynes cling da dua vao hai
nhan t6


"cung" dau tu (tang truOng kha nang san xugt tuong lai) va
su tac Ong taping 116 dPng gifta "cung" va "cau" (tac Ong cUa he s6
tang
t6c). Dim vao hai nhan t6 co ban nay, Keynes da xay dung cac hoc thuyet
hien dai ye
tang
truOng kinh to va cac hoc thuyet ye chu trinh. Nhieu tac
gia sau nay ding dd dung cac gia thiet cUa Keynes de nghien cdu qua
trinh phat tridn
ho4c tang
truOng.
Gang nhu vay, lan dau tien vao nam 1936, nha kinh to hoc Kalecki
Et de cap den nhung khai niem co ban ye hoc thuyet chu trinh dip trC,
'n
hai nhan to "cung" va "cau". Sau do, nha kinh to hoc Samuelson ti6p tuc
nghien cau van de nay. Tiep theo, hai nha kinh to hoc not tieng Harrod va
Domar da phat tridn hoc thuyet nay IT* cach town dien va hoan chinh.
Nhieu nha kinh to da g9i chung day la mO hinh
"Harrod - Domar".
MO
hinh nay da dua ra mot 56 dac tinh cling nhu cac diet' kien cho qua trinh
tang truOng can bang.
1.1. BAN CHAT "KEP" COA DAU TU
.

Mpt nen kinh to luOn luOn chiu tac dpng dong thei cUa
cling va cau
tir qua trinh dau tu, va to goi nom na la
"tac dOng kep".
Qua nhan t6

"cau"
(s6 nhan), dau to xac Binh duoc tang thu nhap
va
tang cau; con qua
nhan t6
"cling",
dau tu ding lam tang truOng nang ivy san xufft.
5
Cau
Xac dinh eau
(s6
nhan)
Tang cau
Al
OQ
~
=
Tang nang ltrc
san xuat
AQ
s
=
/
Nha kinh to hoc Domar da dua ra cau hoi nhu sau: trong dieu kien
nao thi tang cau se tuung thich voi mac tang tra6ng nang luc san xuat do
qua trinh dau tu dem Iai? Neu ta gia thiet he s6 tu ban khOng d6i, voi mac
tang tru6ng nang lkrc san xuat tY le thuan voi mac dau tu va ta c6 Wong
dau
tu
r6ng, theo dinh nghia, bang mire bien thien

A
lacing du trir to ban
thi ne'n kinh to se xuat hien dau hieu cua sir tang truemg.
Ben canh clueing cau, dau tu cung xac dinh auk thu nhap thOng qua
s6 nhan Keynes. Mat khac, tang tru6ng cau phu thuOc vao mac bien thien
trong dau tu. Ta c6 the tham khao hinh 1.1 sau day:
Dau ttr ren2 I
Cung
Tang tradt g tu ban
AK =1

Can
bang
A/
s
— = —
/

v
Hinh /./.
Hai tac nhan ctia dau tu
•
D6i voi
duong
cung:
d6
la tong dciu tu cho phep xac dinh mac dO
tang truOng (/).
•
D6i vai duong

cau:
do la mac tang tru&ng dfiu to Al.
6
Do vay, neu ngay hOm nay ta dau tu mot khoan lien nham dieu
chinh cau theo nang luc san xuat thi ngay mai ta can phai dau tu nhieu
hem n[ra b6i vi chi c6 dau tu moi thuc su lam tang nang luc san xuat
(Domar).
De duy tri mitt can bang giila tang cung va tang cau, ta can phai
thus su quan tarn den dau tu. Do vay, muc dau tu can tinh town hop ILT de
lucrng ta ban va sCrc san xuat se tang tru6ng ved mot tSf le khOng d6i va
bang t37
' s6 gitla lai suat tiet kiem so v6i he se; tu ban. Do vay, khi ta c6
mot khoan dau ta reng thi dieu do c6 nghia la nang luc san xuat se tang
truOng; can bang gida du6ng cung va dung cau chi la can bang

ta
khOng the c6 can bang nao khac ngoai
sit' tang tru'dng da du' c can bang,
ding c6 nghia la khOng c6 can bang
fia.
Trong khi nha kinh to hoc Domar chi
-
mg minh tinh thiet yeti ye van
de 1u9ng tu ban va sac san xuat phai tang trudng theo m0t tS
,
le khOng d6i
thi ngagc lai, nha kinh to hoc Harrod lai chi ra rang, ban chat cna tang
truOng kinh to la khOng on dinh. Tir lap luan nay, Harrod da dat ra hai
cau h6i:
•

MOt la, tinh on dinh cua su tang twang can bang.
•
Hai la, kha nang duy tri mot xa hoi c6 day du tong an viec lam.
1.2. TINH PHI ON DINH CCM TANG TRIfoNG
Bang viec dua ra khai niem ye tang trudng du kien trong qua trinh
xac dinh lacing dau tu, nha kinh to hoc Harrod da rut ra ket luan: ban chat
cUa mei quan he tru6c day xac dinh t57 le tang truOng so \Jai 6/
' le gida lai
suat ti& kiem va he s6 ta ban la khOng on dinh. Tuy nhien, tren thuc
cac bai via dm Harrod van chug cung cap day di' cach chdrig minh ro
rang ve tinh phi 6n dinh cna su tang trudng, them chi Harrod cling khOng
neu duot nguyen nhan cita tinh phi 6n dinh nay. Van de
mJ
nay da du6c
nhieu nha kinh to hoc quan
tarn
nghien cdu tiep va ho da chung minh
dugc rang, v6 thuc chat, tinh phi on dinh Harrod cling chinh la tinh phi 6n
dinh cUa he s6 tang tCic trong thuyet chu trinh: viec dieu chinh kip died he
se dau tu se clan den
ITHIC
Bien d'Ong cua cau va attic Wen clOng cUa nang
luc sari xuat khOng bie'n thien theo cung mot tri s6.
7
•
Tang truerng cau
d
A/ 0,
AQ = =
5

=5%
s 10
Cluing to hay ding nhau xem xet van de thong qua so
.
d6 hinh 1.2.
Gia thia rang he s6 tu ban bang 2% va lai suat tiet kiem rang bang 10%.
Do vay, mdc tang twang can bang tuong img voi 5%. Tren du6ng tang
truOng nay, mdc dau tu rang, mire tieu thu,

san xugt (hoac mcrc thu
nhap) va lacing tu ban ding tang v6i tY le 5% (hinh 1.2a). Neu cac doanh
nghiep quy& dinh dau tu dua tren tee dp tang trithrig du kien la 5% thi
mtic tang truang cung va cau thuc su se dUng bang tY le tang trueng du
kien va bang 5% (tY le tang traCing can bang nay dupe goi la tY le bao
dam - Harrod).
a)
Tang throng dtr kien
AO,* = 5%
•
Dau
tu rang
1=
10%
•

Tang twang nang lkrc
san xugt
AQ" =-
2
/

=5%
b)
Tang twang du kien
z1Q*= 6%
•
Dan to rang
1 =
12%
Tang
throng ming
luc
san xual
AQs2= 6%
Tang twang cau
A/ 2,
AQ
` = =
5
= 25%
S

10
Hinh 1.2.
Tinh phi b6n vting Harrod
a) Tang triang can bang ; b) Tinh phi ben yang.
8
Bay gio to gia thief rang cdc chu doanh nghiep do kien t6c de tang
twang bang 6%. Nhu vay, de nang lot san xuat tang 6% thi tY le dau tu
can phai tang fir 10% den 12%. Mat khdc, de tang 1% nang luc san xuat
(L.

-
mg v6i
Mat
tang truong chung tit 5% den 6%) thi dau tu can phai tang
20%. Do tdc Ong ciia he s6 tang t6c, mac tang them dm eau xuat phat to
ink tang them ciia dau to cling se bang 20% Nhu vay, mire tang truong
cung tif 5% den 6%, con mac tang truong cau tit 5% den 25% (hinh
1.2b). Do (16, cac nha doanh nghiep se can phai tang dau tu de bit dap
mac chenh Lech giCra cung va cau; nen kinh to hu6ng va dat t6i su bong
n6 v6 toc dO tang truong. Nguqc lai, neu t6c de tang truong throe du kien
thap hon 5% thl dieu nay clan den met &rang cau qua yeu kern, va nhu
vay nen kinh to se phai dei mat v6i so suy thodi co the.
Vi du nay da neu re nguyen nhan cua tinh phi 6n dinh: tdc Ong dm
he s6 tang toc dau tu khOng clang met tri s6 vei tdc Ong dia he s6 nay
len tee do tang truong cung (tic Ong dm he se tang t6c) ngoai tar dei
voi met gia tri hang hod rieng biet king v6i the de tang truong can bang.
Do do tdc deng cila he se tang t6c se qua cao bOi hai 17 do: thir nhat, mO
hinh tang truong nay da be qua cdc nhan t6 ngoai sinh cua (long cau (cdc
chi phi cung Ong, xuat khaki, dau to trong nuoc va dau tu thay the); thd
hai, m6 hinh nay cung bO qua th6ng s6 thei han hieu chinh ma thOng s6
nay c6 tdc dung lam
on
dinh hod he s6 tang t6c.
1.3. TANG TRLONG KINH
-
ft VA VleC LAM
Van de did hai ma nha kinh to hoc Harrod neu ra, do la so tic Ong
qua lai gida tang truong kinh to va met xa 110i day du viec lam. Bang cdch
dua ra nhirng lap Juan nguoc lai voi hoc thuyet "tY le tang truong
bdo

ddin"(tY
le nay lam can biting cung va cau tren thi truing hang hod con tY
le tang truong to nhien cho phep duy tri so can bang thi twang lao &Ong),
thi met
nghich ly
xuat hi0: "so dOi lap gida hoc thuyet Keynes va hoc
thuyet
c6
diL".
Neu tji le tang truong bao dam
g„,
cao hon t57 le tang truong to
nhien, nen kinh to c6 the cho phep c6 met t6c de tang truong cao, vi du
9
nhu sau su suy thoai chung tram trong cUa mot nen kinh te", c6 the cho
phep lam giam b6t nan that nghiep:
g = g„,> g„

(1.1)
Nhung khi nen kinh to huong tai viec tao day dU cOng an viec lam
cho ngtred lao dpng thi t9 le tang tru6ng hien hau
g
se bi giai han b6i t9 le
tang tru6ng to nhien. Khi do mac tang truOng thuc se tr6 nen thap hon t9
le tang tru6ng dam bao. Ta nhang nghien can nay, dPng tiled bang each
nhan manh den tinh phi on dinh da dua ra tru6c day, Harrod rat ra ket
luan: nen kinh to se dan dan bi suy thoai do sac cart qua yen.
Ngoai ra, Harrod cling dua ra ket luan: lai suat tiet kiem qud cao
hoac qua thap ding deu gay anh hung tieu cuc den cOng an viec lam cUa
ngithi lao dpng. Tiet kiem se tr6 thanh nhan to tich cuc nen t9 le tang

tru6ng bao dam thap hon t9 le tang truOng to nhien; nguoc lai tier kiem se
tr6 thanh nhan t6 lam suy thodi nen kinh to nen luong tien do tiet kiem
qua du thaa so voi kha nang tang trudng dan s6 va kha nang phat tridn
cUa khoa hoc cOng nghe.
1.4. TANG TRUONG KINH TEVA THol GIAN TAI SAN XUAT TU
.
BAN
Cac 19 luau truck day &roc torn lupc thOng qua viec xac Binh hai
dai lacing lam co s6 cho mO hinh Harrod - Domar: do la
6
k
tang triOng
to
nhic")n
va
6 4'
3
tang triOng
bao
chin?.
Ve mat 19 luan, chung 1a nhang
yen t6 lam co so cho m6i lien he giCra tai san xuat to ban va qua trinh tang
trueng kinh te. ThOng qua viec khai quit hod bang mot s6 nhan t6, nha
kinh td hoc Leontieff da dua ra mot mO hinh clpng voi chat nang tao &roc
nhieu viec lam trong nhang nam 1960. Nhung thu vi nhat van la each tiep
can cUa nha kinh to hoc Von - Neumann vao cuoi nhUng nam 1930 voi
tu9ng sat nhap hai nhan t6 to ban va lao dpng thanh nhan to c6 kha nang
tai san xuat. Sau d6, nha kinh to hoc Brody da nghien cau phat tridn tiep
19 thuyet nay. 14 thuyet da


ra mot 16i giai thIch ttrong d6i hoan chinh
v6 cac giai doan kink nhau cUa qua trinh tang tru6ng nen kinh to dua tren
th6i gian tai san xuat cUa cac nhan t6 san xuat.
Trong inO hinh da nhan to thupc clang Von - Neumann - Leontieff,
tat ca cac nhan to deu c6 kha nang tai san xuat va ky thuat san xuat chi la
10
tdc nhan phu, tY le, tang trudng t6i da cUa nen kinh to duoc xac dinh theo
Cy le &la lai suat tier kiem va he s6 tu ban duoc sir dung (nhu trong mO
hinh Harrod met loaf hang hod).
Khi mot loci hang hoa tit' ban du' dila) thi
gia cna no bang khOng va loai hang hoa do se" /along toe dOng den m6i
pan he _vac dinh 6 le tang trudng tOi da ci;a nen kinh te:
Do vay, tdc d6
tang trudng kinh to se khdc nhau tuY thuec vao mac dau tu rong dugc gibi
han chi theo lacing tich luy tu ban luu d6ng (v6n luu d6ng) hoac nguot
lai, ddu tu rOng lien quan den tang tu ban c6 dinh (v6n co dinh) va tang
von nhan luc (hinh 1.3).
Gia thik rang lai suat tier kiem bang 10%. Trong th6i kY tai thik
xay dung, v6n c6 dinh va luc luong lao deng ky thuat (nhang lao deng c6
trinh de cao) clang du thaa. De tang sac san xuat, ta can phai tich luy to
ban luu deng - von
hat dOng
(tieu dUng trung gian). Neu lacing du tri to
ban luu deng bang 0,5 Lin sac san xuat hang nam thi \Jai lai suat tik kiem
10% se cho ta
mac tang trung
kinh to bang 20%:
0 .1

= 20 %

g

v

0.5
(1.2)
Hinh 1.3.
Tang train
-
1g va tai san xuat ttr ban
Khi v6n c6 dinh khOng du thaa nua nhung ngu6n nhan lac van con
du thaa (khi san xuat khUng hoang thaa, nen kinh to thu6ng dan den du
thaa lao deng, ke ca lao deng có trinh de cao, fir cOng nghiep den nOng
nghiep ),
ddu tu rang se
rot
vao von co dinh (tu ban c6 dinh); nhu vay he
se; to ban (v) se tang va c6 gia tri
tit
1,5 den 2. Lai suat tik kiem rOng
10% se lam tY le
tang
trudng dao deng trong khoang ta 5 den 7,5%. T6c
do tang trung tuong ang v6i thai kY "skr phdt tri6n dieu kS
,
cua nen kinh
te'.
Ne
s
n kinh te

.
thein k
.
57da
duoc biet den v6i cdc nu6c Chau Au va &it
11
nuoc Mat Tr6i moc - Nhat Ban tir sau dai chitin the gioi lan thir hai, va
On day la cdc nen kinh to "m6i n6i".
Trong mot nen kinh to den giai clop
truthig

viec tich luy tu
ban (tich luy von) khOng chi lien quan den tu ban him hinh (von vat chat)
ma con lien quan den von nhan luc. He so tong tu ban tr6 nen lon hon 3,
khi dO t6c dO
tang
tru6ng khOng chi dung 6 mCrc 3%/nam. De don gian
hod van de, cdch phan tich nay nhan manh den yeu t6 th6i gian tai san
xuat cUa cdc thanh phan khdc nhau cau thanh nen von; dieu do khOng
nhirng dem lai mot su giai thIch thd vi ye cdc thei kST tai thiet xay dung va
"su troi day dieu kY", ma con dua ra nhimg tier' de quan trong cho cdc
quan diem trong hoc thuyet tang tru6ng not sinh.
12
2
NGUYiN TAC VANG
CUA TANG TRU'&NG
VA VAN De PHAN CHIA THU NHOP
Nhirng IY luan dm Harrod ve kha nang tang tru6ng dinh ky Xi lam
nay sinh hai van de khdc bier, d6i lap voi cdc hoc thuyet kinh to till& do.
D6 la:

1.
TInh on dinh dm tang tru6ng phat sinh bei su tdc d9ng tiling 116
giira s6 nhan va gia t6c;
2.
Kha nang dam bao mot xa hei day du cOng an vidc lam, diet.' (16 c6
nghia la tY le: tang tra6ng bao dam can phai du6c can bang hod, ma
tY le nay la ket qua cua khuynh twang tiet kiem, dm he s6 to ban;
va tY re tang tra6ng ter nhien la ket qua cua su tang dan s6 va t6c d9
phat tridn khoa hpc cOng nghe.
Van dd thin nhalt ma hpc thuyet chu trinh de cap den la su tang
tru6ng theo chu kY. Win de dill hai se tr6 thanh van de
/Net ye:u
cua
h9c thuyet tang tru6ng can bang ma chung to se xem xet ngay sau day.
Phat trien Va0 nira cu6i nhimg nam 1950, hoc thuyet nay nham giai
thich dac diem mang tinh chu kY cua qud trinh tang trithng kinh te.
Dac biet tir sau chien tranh the giai thu 2, do su phat trien khd "ngoan
muc" trong giai (loan tai thiet va xay dung lai nen kinh re", nhung cau
hOi ma Harrod dua ra ve nhiing nguy co co the cua n6n kinh to chua
ducc quan tam dking mac - tham chi chua duoc (16 cap tad.
Ngtroc lai, cac khai niem ma Harrod va Domar dua ra nhan manh
den su khOng tuong help glib tY le tang tru&ng kinh to (tY le nay
la
ket
qua cua tie't kiem va cua khoa h9c cOng nghe) va tY le tang tru&ng to
13
nhien (tY le nay phai dam bao day dU viec lam). Neu sir' tang trung kinh
to lam can bang hai tY le nay thi dieu do c6 nghia la nen kinh te
linh hoat
lion nen kinh to theo mO hinh Harrod - Domar.

Dtra tren nhiIng kien fink cna hoc thuyet sue san xuat bien, hoc
thuyet tan c6 dien ye tang tragng cUa Solow, Swan va Tobin da dua ra
khai niem ye tinh linh hoat ben canh ky thuat san xuat tilt la tinh linh
hoat cUa he s6 tu ban (he s6 v6n v). Nhu vay, theo quan niem
ye
tinh linh
hoat nay, dieu do chinh la nhang
plicin ling qua lai giita gia cd, hong, va
loi ich. Ccic ninth to nay clang mgt vai tra quan trong trong qua trinh
dieu
chinh hoc thuyet tan ca' dien (Solow - 1956).
Theo quan niem ve sir chenh lech mire phan ph6i thu nhap, dieu do
cling c6 nghia la viec tiep can sau sac vain de cita phai Keynes m6i da
phan tich sir dieu chinh tY swift
bdo dam
theo ty le tang trugng ter nhien.
Trong phan tich cUa Kaldor (1955), viec tich luy tu ban khOng con la ket
qua theo khuynh huang khOng doi nham tiet kiem thu nhap; ngugc lai d6
la t6c de tich luy ma no xac dinh lai suat tier kiem theo sir thay d6i chenh
lech mire phan ph6i thu nhap. Do vay, theo phan tich cUa Keynes, s6 nhan
dau tu la nen
tang cua hgc thuyet viec lam trong thoi kS) ngan ban va tinh
trang xa h gi Mien (Ong On viec lam; dung thai la
nen
king cna hoc thuyet
phan chic thu nhap trong thoi ky dai han va tinh trgng A-c7 hoi ddy dii
tong On viec lam.
Do vay, theo hai each tiep can nay, van de xac dinh each phan chia
thu nhap da (live dat ra. Van de nay da tr6 thanh tieu diem cita nhiing
cuec tranh luan giira hai trugng phai tan c6 dien va hau Keynes trong

nhilng nam 1950 va 1960. Hai hoc thuyet nay se giai thfch hai clang dac
tit
-
1h quan trong: d6 la
tinh on dinh cfia each thti'c phan chic thu nhap va
tinh do dinh cna sit' tang trtOng.
2.1. MO HINH TANG TRUCiNG TAN CO DIEN
Khi cac nhan t6 san xuat c6 kha nang thay the thi he s6 tu ban troy
thanh ham cUa kh6i lacing tien te (cueng d6 tu ban). Trong theri ky khoa
hoc ky thuat kern phat trien, sue san xuat trung binh cUa tu ban
(1/v = nghich dao cua he s6 tu ban) va sue san xuat tu ban bien la nhfing
ham phi tang trugng kh6i lacing tien te (luang to ban/dau ngugi). Khi tai
14
suat tiet kiem khOng doi thi tY le tang truOng
bdo ddm (sly)
cling la mot
ham phi tang truOng kh6i lung tien te. Do vay, tinh linh hoat cUa ky
thuat san xuat cho phep can bang tY le tang truang
bdo ddm va
6'i
le tang
tra&ng tu nhi'en (hinh 2.1). Neu ban dau nen kinh to có mot lacing to
ban/dau ngued qua dia) (diC,rn A - hinh 2.3), thi tY le tang truOng
bdo
ddm -
c6 nghia la tY le tang truOng to ban - se cao hon tY le tang tru&ng
sire lao &Ong va luting to ban/dau ngued cling se tang. Khi dO nen kinh to
se di chuyen den mac tang tru6ng can bang (diem E). Khi luting to
ban/dau ngtrOi ban dau cao hon gia tri can bang thi hien nhien van de, se
di theo chieu huong nguoc lai.

Ty le tang tragng
A
Ty le tang throng ta ban
13% 14 tang tragng darn bac, sh
,

Ty le tang
trugng cua
kh6i lirong
tu ban
theo &in
ngagi
k
0

k*

Kh6i luting tu ban
Luting tu ban/dau ngugi
k
Hinh 2.1.
MO hinh tang truang tan
co
din
Nhu nha kinh to hoc Solow da chi ra, each dieu chinh au& day
&roc thuc hien
ngni
bang each dua tren mac chenh lech A phan chia thu
nhap. Khi luting to ban/ dau ngubi qua thap (diem A - hinh 2.1), thi sac
san xuat bien to ban - c6 nghia la tY suet lgi nhuan - se cao hun tY suat

loi nhuan ling v6i str tang tru6ng can bang. COn d cac th6i IcS7 khac, mac
tien luting thuc lei qua thap va ky
-
thuat san xuat tu ban chua phat then
day clU. Nhung viec tang luting tu ban/dau nguM
se
lam tang twang sac
15
lao d6ng va muc Wong thuc d6ng th6i lam giam sac san xuat Bien tu ban
(tY suat 10 nhuan) cho den khi nen kinh to dat toi dung tang trudng can
bang. D6 linh hoat cUa luong cho phep dieu chinh trong su6t khoang th6i
gian dai de darn bao mot xa h6i co day dU c6ng an viCc lam. Neu mut
luong thuc
cMig ididc
thi tY le tang trtrOng kinh to (tY suat
bdo ddm)
se
cao hon tY le tang sac lao Ong. Di6u nay se gay ra sir thie
-
u tang tru'Ong
v'e Inc lacing nhan c6ng. Su thieu hut nay tat yeu se keo theo sy tang cao
mire luong thuc ma no se di chuyen den dung tang tru6ng can bang moi
(diem E - hinh 2.1). Chting ta se xem xet mo hinh phi can bang trong
phan sau (m6 hinh nay lien quan den de khOng linh hoat tuong d6i cUa
mat tin Wong thkrc).
MO hinh tang trtt6ng tan
c6
din :
Ham san xuat v0 nang suat khOng dPi:


Q = F(K,N)

(2.1)
trong do:
Q -
ham san xuat;
K -
v6n;
N -
lao (16ng.
Bang each chia cho s6 lao Ong, ta xac dinh dupe m6i quan he giira
s6 luong san pham/dau nguoi q
va
Wong v6n/dau ngu'6i
k.
1
K
q =
Q
= F

= f (k )

(2.2)
N

N
(clang nay da dugc trinh bay 6 hinh 2.3).
Goi : ii - tY le tang truOng skit lao Ong;
s -

lai suat tiet kiem;
tY le tang truOng tu ban (tY le tang tru6ng v6n - tY suat bao dam) &roc
tinh theo cOng
1
dK

1 = s
Q
K dt
(2.3)
16
1 dk
=
S
k dt
hay dk
f (k)_
n

k
sf (k ) — nk
dt
(2.5)
va tY le tang tru6ng to ban/dau nguOi se bang
1
dk

s
Q
— n

k dt
hay Q

f (k
K

k

(2.4)
(ham phi tang truOng
k,
khi
f
thoa man dieu kien Inada
f" <0, f'(0) 00 , f'( Go) = 0).
Do vay ham vi phan xac dinh mire dO tien trier' cUa luting to ban/
dau nguii
DOng that tuong Ong voi phuong trinh 2.5 ducic bieu din hinh 2.1.
—
s
=
s
f (k)

(2.6)
v

k
Nguyen tac yang
Trong truOng hop tang truong can bang

(k
khOng d6i), thi Wong to
ban/dau nguoi (lacing von/dau nguOi) va mac tieu thu theo dau ngubi
duoc xac dinh theo cOng thCrc sau:
sf(k) = nk

(2.7)
c(k) = f(k)— ,sf(k)

(2.8)
Tir (2.7) va (2.8) to rut ra phuong trInh:
c(k) = f(k)— nk

(2.8a)
Mire tieu thu theo dau nguii se lon nhiSt khi
f'(k) = n
(nguyen tac
yang).
Hinh 2.3 bieu dien siic san xugt /dau nguii
f(k),
luting dau to/dau
nguii
(nk) va
mire tieu thy/dau nguii bOi ham s6 luong to ban/dau ngtrOi
k
(ltrong von/dau nguii) cUa che dO tang truOng can bang.
17
Da'y nhanh tarn thoi ctia tang
twang


* Lugng tu ban/dau ngugi
n
2.1.1. flac tinh nhgt thoi cua skt tang twang khi khOng co
nhang tio'n b§
ye
khoa hoc cong nghe
MO hinh tang truCing tan c6 dien con ton tai rat nhieu van de ma
chung ta se xem xet tiep thOng qua hoc thuye't ye tang tru6ng nOi sink.
Nhung dieu lam cho chung ta quan tam nhk, theo quan diem ciia hoc
thuyet tang truOng, do la viec tang tY le tiet kiem khOng lam thay d6i t6c
de tang tru9ng cUa nen kinh

no chi lam thdc day nhat th9i su tang
trtthrig 'sari xuat va tang kh6i Wong tu ban nham bat kip theo dubng tang
r;.trudng tu ban cao hun, co nghia la du9ng bieu dien lung tu ban (lacmg
'tier] to ban)/dau ngueri tang cao hon (hinh 2.2). Tren dubrig tang truang
nay, mac san xuat tinh theo dau nguoi cling se tang len.
Ty le tang trugng
s„

s
1

k,

k,
Hinh 2.2.
Tac Ong
cua
vi0 tang

07
'
le
tiet
kiOn
2.1.2. Nguyen t'ac yang
Trong qua trinh tang truerng deu theo chu ky, lacing dau tu/dau
ngueri se tY le theo 1u9ng tu ban/dau ngued: de tang gap dOi lugng tu
ban/dau ngueri thi cling can phai
tang
ggp
dOi lacing (Mu tu/dau ngued;
clieu do du9c the hien qua clop thang OC (hinh 2.3), trong d6 (10 d6c cOa
duong thang nay bieu dien tY le tang twang cUa nen kinh te. Luvng san
pham/dau nguei ding tang theo v6i luvng tu ban /dau ngued nhung sac
san xuat bien cUa von lai kh6ng tang tru&ng, de &lc cua throng cong OBC
18
San xuat theo dau nguoi
(k)
B*
No

Dau tu va tiet kiem theo dau
ngugi
(nic)
A*
Mac
tieu
dung
theo

dau
nguoi
•
{
giam trong khi lacing tu ban theo dau ngu9i tang. Voi met tY le tiet kiem,
lumg to ban/dau ngubi va lumg dau tu/dau ngubi cho truac, thi mac tieu
thu linh theo dau nguOi du9c bieu dien 139i (loan thang AB. Neu tY le tiet
kiem tang thi mac tieu thu/dau nguoi ding tang, vu9t qua mac giOi hen
toi da (A*B*) va se to triet fieu diem C - diem ma tai do san xuat se
hoan toan ducic tiet kiem va (lucre danh cho &du tu.
Do vay se ton tai met du9ng Lich luy; clueing nay keo theo mire tieu
thu tei da (finh theo dau nguoi). Mac lieu thu nay dat tad diem A* - diem
ma tai dO sac san xuat bien tu ban (de dee cna clueing tiep tuyen tai diem
A) se bang tY le tang traOng dm nen kinh to (de doe cua doan thang OC).
Mat khac, (Ming Lich luy keo theo mac tieu thu cao nhat linh theo dau
nguoi aing cllinh la tY suet 19i nhuan (hoac tY le lei Ich) hay bang CY le
tang trueng. DO chInh la nguyen tac yang (ducic thiet lap bOi hai nha kinh
to hoc Phelps va Desrousseaux). Khi tY le tiet kiem thap hurl tY le dm
nguyen tac yang (tY suet 1cii nhuan hoac tY le lei Ich cao horn tY le
tang
trueng), thi viec tang lei suet tiet kiem se lam tang mac lieu thu theo &du
nguOi. Con khi tY le tiet kiem cao hun tY le dm nguyen tac yang, thi se
xay ra tinh trang lacing tu ban tich luy qua nhieu: viec giam ty 1C tiet kiem
se khuyen khIch tieu dung, cho phep
tang
mac
lieu thu theo dau nguoi.
San xuat, dau tu va
tieu
dung theo

dal] ngugi
0

k

k*

Luting tu ban theo dau ngubi
k
Hinh 2.3.
Nguyen tat yang
19
2.1.3. Nhang tien b§ khoa h9c k9 thuat
De co the mO ta tien trinh cua nen kinh to hien huu, ta can phai tinh
den yeu to
luoig san plidm binh pan theo ddu ngffoi
tang trong mot thOi
- do la d6i tugng cUa nhting tien bp khoa hoc ky thuat. De ton tai
mot the dp tang tragng can bang theo lai suat tiet kiem khong d6i thi
khoa h9c 1ky thuat can phai nam dugc chin
khoa clia Harrod,
co nghia la
khoa hoc ky thuat chi lam tang nang suat lao dpng. Trong gia thiet nay,
luting to ban binh quan theo dau ngugi, luting san pham binh quan theo
dau ngued va mdc lieu thu binh quan theo dau ngued tang theo t6c dp phat
tri6n cUa khoa hoc ky thuat. Nhu vay, viec phan tich trugc day van co the
chinh xac bang cach ta sda doi, dieu chinh lai sac lao dpng phb hop theo
nhang tien bp cUa khoa hoc 1(5"/ thuat, có nghia 1a ta do sdc lao dpng bang
don vi hieu qua.
2.2. LAI SUAT TIET KIN VA CACH PHAN CHIA THU NHAP

(KALDOR)
Nhang mO hinh chat luting cua phai
sail Keynes
va mO hinh phat
tri6n ban dau cUa Kaldor da de cap chinh xac hon den mot cach nhin d6i
lap voi nhang mO hinh co dieu chinh truoc day. Kaldor gia thiet rang
khuynh huong tiet kiem tien (khuynh hung tiet kiem to ban)
s,.
cao hon
khuynh huang tiet kiem nhan cOng
s„,.
Do do, tS7 le tiet kiem se la mot
ham tang tru6ng phan lqi nhu4n cl4t &roc to khOi luting san phtim trong
nuot va t5
,
le tang tru'O'ng bao dam
(sly)
ciing trd thanh mot ham tang
tweing t57 suat loi nhuf
.
in (hinh 2.4). Do vay, se ton tai mot gia tri cua t57
suat loi nhuan sao cho thOng qua gia tri nay nen kinh to se tang trtro'ng
can bang trong mot xa hpi có day dU viec lam (diem E - hinh 2.4).
Mat khac, su can bang nay la on dinh. Neu ty suat Igi nhuan cao
hon gia tri can bang thi tY le tang truOng bao dam se cao hon tj le tang
twang to nhren. Neu nen kinh to tang tragng theo t57 le tang traCing bao
dam thi se xay ra hien along thieu tang trugng ve nhan cOng lao dpng va
do vay (long luting se co khuynh hung tang len. Mtic tang tien luting
thuc khi dO se keo theo si suy giarn ve tY suat lqi nhuan, lam su tang
trugng tY' le bao dam bi


lidm:
di chuyen den diem can bang mdfi E.
20
Ty le tang trucking
r

r*

r,

Ty le lqi nhup
r
Hinh 2.4.
Tang trtrOng va phlin chia thu nhUp trong mo hinh Kaldor
Qua do, to ding co the dua ra nhirng khdi niem ban dau ye hoc
thuyet phi can bang cung - cau tren thi twang hang hod. Neu khong ton
tai mot sty can bang gida cung va cau, thi t57 le tang tru&ng co the ducrc
xac dinh giira tY le boo dam va t.57 le to nhien trong kS/ ngdn han (diem
A
l
-
hinh
2.4).
•
g<g„,:
Thing du cung tren thi tru'ong hang hod.
•
g>g„.:
ThOng du cau tren thi treing lao &Ong.

Thong du cung tren thi trubng hang hod keo theo sty suy giam ve gid
san xuat; thong du cau tren thi tru6ng lao Ong keo theo su
tang
Wong
danh nghia. Trong ca hai tru'ing hicrp nay, dieu nit ra la
-
su tang tin Wong
thkrc va sty suy giam tY' suit lqi nhuan se clan den trang thdi can bang.
Trong treing hcv nguqc 'di, tai di6rn
A
2
,
thing du cau tren thi trubng
hang hod va thing du' cung tren thi trueng lao long lam tang tji suet lqi
nhuan va ding clan d6n di6m can bang E.
21
3
PHAN TICH THEM
VCCACH NAN TAN CO DIN
Nhirng nam 1960 da c6 nhang kr& phdt trien dai ve ly luan va thuc
tin d6i v6i mO hinh tan c6 di6n: t6i uu hod cdc the (10 tang truoug, cdc
mO hinh to ban da cap, phan tich cdc nhan t6 tic Ong d6n
sir tang trtrong
trong

kST dai
3.1. TICH LUY T61

T61 LIU XA HOI VA
-

r6i
U'U

NHAN
Trong
mO
hinh tang traong
tan
c6 dien duqc phat trien vao giira
nhirng nam 1950, tS le tiet kiem dupt gid thi6t la khOng d6i (sau nay,
Harrod va Domar deu sit dung gia thi6t Keynes nay). VI vay, viec ltra
chon tjT le tiet kiem bang bao nhieu la van de gay tranh cai gida cac ca
nhan va xa hOi, gifia mire tieu dung hien nay va mitt tieu dung tuong lai.
Trong qua trinh nghien cdu hoc thuye't hien dai ve tiet kiem, ciic nha kinh
to hoc da dua tren su lua chon mang yeU to vat chat cua cdc 110 dan cu
(dac biet 1a d6i v6i hoc thuy6t ve chu kS/ song cua Modigliani); nhirng mO
hinh tich 1uy t6i uu se dua.ra nhting cach thdc lua chon nay.
Trong qua trinh phat trien hoc thuyet, nha kinh to hoc Ramsey
(1980) da c6 cOng lao to Ion vai 16i giai thich quan trong mang tinh thuc
nghiem o Philp bang viec xac dinh tji suit hien dai hod theo chuong trinh
tang trueng kinh te". Ngoai ra, 1T thuya nay ci:ing dan thin duqc thay the
b6i hoc thuye't t5
,
le tier kiem ngoai sinh va thi6t lap mot m6i
truCing quen
thuOc mod cUa cac hoc thuye't tang tru&ng not sinh.
23
3.1.1. Tang traCing
t6i
au va nguyen tac yang du'oc di6u chinh

Win de gay tranh cai gilla mire tieu dung hien tai va mdc tieu clang
tuung lai co the duqc torn luqc bang hai tham s6:
•
Thu nhat: lqi ich tirc thi cUa tieu dUng.
•
Thd
hai: lgi ich
tdc thed nay duqc hien tai hod theo mot ty suat
nhat dinh trong ham lqi ich c6 yeu to thi gian, c6 nghia la ty suat
hien tai hod la t.57 trong arcing d6i cUa lqi Ich hien tai va tuong lai.
T57 suat nay duqc ky hieu
0-
la 67
' suat uu
dai hien tai.
Trong giai doan tang truCing can bang, t.57 le
tie
-
t
kiem kh6ng dOi va
to c6 ham uu dai tai thai diem hien tai. Khi xa hOi ton tai mot nguyen tac
dun gian (nguyen tac Ramsey hoac nguyen the yang duqc dieu chinh) lam
eau not giira sue san xuat tu ban bien \Tali t57 le tang trueng cira nen kinh to
thi sue san xuat tu ban bien se bang t57 le tang truong (ma tY le nay tang
theo ty suat uu dai hien tai).
f'(k) = g + B

(3.1)
3.1.2. T6i u'u x5 h§i va
t6i

au to Wan
MOt van d6 quan trong khac cua mO hinh tan
c6
didn 1a tit
-
1h tuung
throng giira t6i uu xa hOi va sir can bang c6 canh tranh. Neu cdc 110 dan cu
xdc dinh mire phan chia tieu thu - tiet kiem cua ho bang each t6i da hod
lgi ich vat chat trong dieu kien han the v6 ngan quy7 thi tS
,
' le sinh led ar tai
san tai chinh cua cac 110 dan Cu nay (tY suat lqi Ich r) trong truemg hqp
tang tru6ng can bang se bang tong hai dai luong: qi le tang tru6ng va t5/
suat uu dai hien tai:
r = g + 0

(3.2)
Mat khdc, viec t6i da hod lgi nhuan trong cac doanh nghiep duoi
diet' kien co ham san xuat se dan den six bang nhau gitia sue san xuat to
ban bien va ty suat lqi ich:
fik)=
r

(3.3)
24
Wong s'an phgm
binh guar' theo
d6u
f (k,)= c, + fit' + nk
dt

Muc Tau
thy
binh quan theo
cl6u
ngua
D6u
tu'
binh quan theo
dgu
ngu'di
(3.5)
Do vay, sir can bang mang tinh canh tranh se den den viec t6i tru xa
hei c6 dac tinh du is bieu dien qua bieu thirc can bang (3.1).
Tich luy toi uu va nguyen tac Ramsey
V6i cdc cid lieu da cho 6 phAn truck, ta c6 mdc can bang cna thi
tru6ng hang hod ductc bieu dien nhu sau:
Q,=F(K„N,)=c,+
ddK

(3.4)
Cung lao Ong
N,
(bang cdu lao deng) tang theo tY le
n.
Bang each
sir dung cdc bi"en binh quan theo ddu ngu6i, m6i quan he tren c6 the ducfc
viet thanh:
Bien a
lung ddu to binh quan theo ddu ngkr6i bao gom hai s6
hang: ddu to gia tang

nk,
va dau to lam tang lacing von (1u6ng ta ban)
dkl dt.
Dung tich lu
-
y t6i uu dat dude beri he plurong trinh sau:
m .ax fu(c)e
°
rdt;u'> 0 ,u" <
0
0
fi
t
'
f(k,)=c,++ nk,
Dao ham bac nhat, ta suy ra dieu kien Ramsey
f ' (k,) — (n + 0) = — u" dc
u dt
Trong the d6
tang
tru6ng
can
bang (trang thdi on dinh d6i v6i cdc
bien giam), tY le lei suet bang tY le
tang tra6ng (tiT
le nay tang theo ty suet
uu dal hien tai, phuung trinh 3.7 trd thanh "nguyen tac yang chive dieu
chinh").
(3.6)
(3.7)

25
c = c,k = k,


dc
di, =
0

{(5)
.
/
1
(0=
n +
(6)c = f (k) — nk
Lacing du trir lien to tu ban k trong trueng hop tV' sugt uu dai hien
tai
6
1
>
0 se nhO hon Wong dir trir tien to to ban
k
tuong ung voi nguyen
tac yang
(k*
khif'(V) =
n).
Khi 1/8 khOng dei (ham s6 c6 de co dan thay
the c6 yeu to thi gian khOng dei) thi nguyen tac Ramsey tr6 thanh:
c

u
(c, ) =
(
'

1
.1
(k)— (n + 6
)
= a
1 dc

1 — a
-

c,
Cu6i cung, voi sir tien be cua khoa hoc cOng nghe lam tang kha
nang lao deng (7), nguyen tac yang dtroc dieu chink tre thanh:
F'(k) = n+ 8+ o7

(3.10)
Khi de co dan thay the bang met don vi (u=log(c,)), thi sdc san xua:t
to ban bien bang t/ le tang trudng
(n+y)
(6% le nay dtroc tang theo ty suat
uu dai hien tai).
3.1.3. SI! ua thich thai di6'm hien tai va kta ch9n clueing tang
tru'ang
Ua thich la
met khai niem daec dung lan dau bei cac nha kinh to

hoc tan c6 dien sau do duec dung kha ph6 bien trong cac tai lieu kinh t6
hoc hien dai. Day la met khai niem thuec pham trY tam l5T, rat MI6 do dac
va Wong hoa, tuy nhien lai rat tien 19i cho cOng tac nghien dm.
Trong thuc t6, cac chu the tham gia thi tnthng (ngtred tieu dung, cac
t6 chic hay doanh nghiep ) c6 xu huong
quan tam 'Mien den hien tai.
Nhu vay, khi cac nhan to c6 sit u'a thich th6i diem hien tai, thi throng Lich
luY Cei uu ttrong dng voi khei 'Yong tu ban (khei luting tien tO, tj, le ti6t
kiem va mac tieu dung binh quan lien &du ngtrei se th4 hon so voi
dveng "nguyen tac yang". Khi suc san xugt tu ban bien cao hon ty le tang
tra&ng, thi viec tang 'di swat tiet kiem o ky dai han se lam tang mire tieu
the binh quan tren dau ngt.r6i. Tuy nhien, qua hinh 3.1 to nhan thay rang 6
kST ngiin han, yiec giam mac tieu the binh quan theo dau ngubi limit khi
c6 skr thtic day tam th6i sir tang tru6ng san xuai se dtm den mac lieu dung
binh quan lien dau ngtreci ti6p tvc tang cao ho'n nira.
(3.8)
(3.9)
26
Neu tY trong cdc mac tieu dung along lai la dOng nhat trong ham
19i ich co yeu t6 tiled gian
(0 =
0), thi cdc tdc nhan se luen
thick
dung
tich Iuy. Dugng nay &tin den mdc tieu dung binh quan tren dau ngugi cao
nhk (nguyen tac yang)

neu lugng tieu dung tam th6i bi mat di thi
no lai dugc bit dap lai bgi lgi nhuan tir tieu dUng tuong lai. Nhu vay, gia
tri B ket hgp voi du'gng tang trugng la tY suet hien tai hod. Ty suet nay

lam can bang gid tri dugc hien tai hod ciia viec mat di lugng tieu dung
ngin han va lgi felt dugc hien tai hod cita lugng tieu diing tuung lai.
Tieu Stag theo dau ngtrgi
•
Tieu dung t6i da
Nguyen tac yang
r =
g
Tien dimg tgi tru
r = g +
Lgi ich dui tieu
diing dai han
Su mat trang cua tieu
dung ngan han

►
ThOi gian
4 Tang
lei suet tiet
kiem

►

Hinh 3.1.
Tich luy t6i uu
3.2. PHAN TICH CAC NHAN TO TANG TIRtioNG
Gia sir c6 met ham san xuCit vai cdc nhan t6 co the thay the dugc.
Ghi thie't
nay dugc xem xet kyi tren co so phan tich sir tang trugng tuy
thuec vao rink de (long gop cita timg nhan to san xuk.

Nat cdc nang suet guy me ding bang met don vi, va cdc nhan t6
san mak dugc tra luting theo sac san xuk bien thi tY le tang trugng san
xugt la tong cdc deng gop cUa tirng nhan to, dugc xric dinh theo phan tra
tin luting c6a tong nhan to san xuk.
•
Neu to ky hieu
a

-
phan Igi nhuan;
(1 -
a) -
chi phi lao Ong;
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