Kxsiii Tit, VA ftiuLv I.Y
MQT NGHIEN CtfU TH^C NGHigM VE NHU CAU THjT, CA d KHU V^C THANH THj VA NONG THON Vl|T NAM
Pham Thanh Thai *
©
Ngay nhan: 2 0 / 6 / 2 0 ^ 2 M a s d : 1.TKPT
Jit khda: He soco dan MarshalTian, Hickslan, he thdng ham cau, hoi quy kiem duyet, mo hinh LA/AIDS, phan tich nhu cau thit, ca, thanh thi, ndng thdn, ViPt Nam.
/p ai viet bao cao ket qua nghien cdu nhu cau tieu ddng cac san pham thit va ca cho khu vuc thanh (/--> thi va ndng thdn Viet Nam bang md hinh AIDS (Almost Ideal Demand System). Nghien cdu sd dung dO li$u thd cap. loai dO li$u cheo duac thu thap td cupc dieu tra ve mdc song cua hP gia dinh d VIPt Nam (VHLSS 2008) bdi Tong cue Thong ke Viet Nam nam 2008. Phuang phap hoi quy kiem duyet (cencored regression) cho he thP'ng cac phupng trinh dUpc sd dung. He thd'ng ham cau hai buPc dupc ddc luang. Trong giai doan thd nhat. ty le Mill nghich dao (Inverse Mill Ratio - IMR) ddPc udc lupng bang each sd dung md hinh hoi quy probit. Ben giai doan thd hai. bien IMR tinh d giai doan mpt dupc them vao mo hinh AIDS de udc lupng dp co dan cua cau cho cac mat hang thit va ca. Miic tieu cua nghien cdu nham uPc lapng cac loai he soco dan cua cau khac nhau cho cac mat hang thit va ca d khu vuc thanh thi va ndng thon Viet Nam. Ket qua nghien cdu cdng cd the cung cap mdt bang chdng thdc tien cho cac nha lam chinh sach de thiet ke chinh sach ve thuc pham d Viet Nam..Cac tham so cua mdhinh udc lapng dapc sd diing de tinh cac he soco dan cua cau theo gia Hicksian va MarshalTian va he so co dan cua cau theo chi tieu. Ket qua cho thay he sP'co dan theo chi tieu (thu nhap) cua thit Ipn va thit ga 6 khu vuc ndng thdn nhd han so vdi khu vUc thanh thi nhdng he soco dan theo chi tieu (thu nhap) cua thit dd va ca 6 khu vdc thanh thi lai cao han so vdi khu vdc nong thdn. DPI vPi ca hai khu vdc, thjt lan va thit ga la hang hoa thdng thudng, trong khi do thit bd va ca lai la hang hda xa xl
1. Gidi thi^u
Phan tich nhu eau tieu dung la mdt trong nhQng chij de quen thudc nhat trong kinh te hpc Qng dung.
Cac nghien cQu trUdc day thudng sQ dung md hinh phuong trinh don de udc lupng nhu cau hang hoa ciJa ngudi tieu dung. Hdn nOa. eac dac trUng md hinh phuong trinh dPn dupc de cap ban dau chu yeu la de udc lupng dd co dan va danh mdt it su chu y den ly thuyet tieu dung (Deaton va Muellbauer 1980b).
Trong nhQng thap nien gan day, phan tich nhu cau tieu dung da cd nhQng each tiep can mdi theo hudng md rdng mang tinh he thd'ng. Cach tiep can nay dam bao he thd'ng cau la phu hop vdi ly thuyet tieu dung, vl eac ham cau dupc xay dung dua tren ly thuyet ve su lua chpn cua ngUdi tieu dung. Mdt trong nhQng md hinh duoc Ung dung rpng rai dd'i vdi cae nha nghien ciXi !a md hinh AIDS (Almost ideal Demand System) cua Deaton va Muellbauer (1980a)
Nghien cUu ve cau true cau thyc pham da dupc tien hanh ra't pho bien d tren the gidi, dac biet la d cac quoc gia phat trie'n nhung tai Viet Nam thi cd rat it cac nghien cQu ve van de nay. Mdt sd nghien cdu gan day sd dung dQ lieu cheo trong phan tich nhu eau thUc pham d Viet Nam bao gdm Linh Vu Hoang (2009), Canh Quang Le (2008), Haughton
& ctg (2004), Thang va Popkin (2004), Benjamin va Brandt (2002). Minot va Gdetti (2000). Figule (2003) analyses vegetable consumption behav- iour in Vietnam, while FAQ (1999) considers the relationship between food consumption and nutntionNghien cUu nay sd dyng md hinh AIDS de ude lupng he thd'ng ham cau thjt va ca cho khu vuc thanh thi va ndng thdn Viet Nam, thong qua
* ThS Trudng Oai hoc Nha Trang
86 49/2012 ^iiiitfng n/lai is
K I M I I E VA ^AX J.Y
dd ude luong eac he so co dan cua cau theo gia, theo thu nhap va so sanh he s d co dan gida khu vuc thanh thi vdi ndng thdn. Ket qua nham cung cap cac ket qua mang tinh thuc tien de giup cae nha hoach dmh chinh sach cd eo sd khoa hoe hon trong vi#c thiet ke cac chinh sach lien quan.
2. Cd sd ly thuyet va phUdng phap nghien ctiu Md hinh dupc ap dung trong nghien cQu nay la md hinh AIDS (Almost Ideal Demand System) cua Deaton va Muellbauer (1980a). Md hinh AIDS la mdt trong nhQng dang ham pho bien nhat dUpe sd dung de Udc lupng he thdng ham cau. Mdi phUPng trinh ham cau trong he ham cau AIDS cd the dupc viet nhu sau:
= a,-hZ/.jlnpj-
Mn-U, (1)
Trong dd: W| la ty phan chi tieu cho mat hang i, Pj la gia eua mat hang j , x la tong chi tieu cua cac mat hang co trong he thdng, y la he so cua bien gia, p la he sd cua bien chi tieu (thu nhap) va P la chi sd gia dupc dmh nghTa d phUdng trinh (2).
\nP = ao + S a , In;?, -i--SZr,j ^np, [npj (2)
De dam bao tinh ben vQng ve mat iy thuyet cho ham cau, Deaton va Muellbauer (1980a, 1980b) da nghien cCiu va dua ra cae rang buoc cho md hinh AIDS, cu the la:
Tinh cpng don:
Z«,-^Zr,-0'ZA = o t3)
Tinh ddi xdng: /i, ^ Vj, (4)
Tinh ddng nhat: Y./,,=^ (5) He sd CO dan theo ehi tieu (thu nhap) dupc tinh theo cdng thUc sau:
A, = \ + p,l\\, (6)
He so CO dan^ theo gia rieng dUpc bieu dieh theo cdng thQc sau:
Va he sd co dan theo gia cheo dUpc xac dinh theo cdng thdc sau:
£ " , j = 0 ' , j - w , > f i i ) / w , (8)
Ham cau AIDS la tuyen tinh ngoai trd dang ham translog cua chi s d gia InP. Trong hau het cac nghien cdu Qng dyng, dd khac phuc van de phi tuyen va lam giam cac anh hudng cua hien tuong da cdng tuyen trong md hinh. cac nha nghien cUu thudng sU dung ehi so gia Stone {\nP = Y,,w, li) nham tao ra he thdng tuyen tinh (Cach lam nay cung dupe de nghi bdi Deaton va Muellbauer, 1980a, 1980b). Md hinh AIDS vdi chi sd gia In P - X , w, I n p, dUdc goi la md hinh AIDS xap xi tuyen tinh va dUpc ky hi^u la LA/AIDS (Linear Approximate Almost Ideal Demand System). Tuy nhien, ehi so gia Stone khdng thda man tinh chat CO ban cua sd chi sd, bdi vl ehi sd gia Stone la khac nhau khi cd su thay ddi trong cac ddn vi do ludng eua gia ea, Mdt trong nhQng giai phap de hieu chinh don vi cua sai s d d o ladng la chuIn hda gia ea bang each chia gia ca eho gia tri trung binh mau cua nd (Chern & ctg, 2003). Moschini (1995) de nghi sd dung chi sd gia Laspeyres vdi muc dieh khac phuc van de sai sd do ludng nay. Chi sd gia Laspeyres cd the dUpc bie'u dieh nhU sau:
ln(P^) = Xw,ln(p,)
(9)E„ = -\+yJw,-/^_
(7)Trong dd: w , ia phan chi tieu trung binh ciia hang hda i. Nhu vay. trong nghien cQu nay chi so gia Laspeyres duoc sCf dung de thay the cho chi so gia Stone trong udc lUpng md hinh LA/AIDS.
Phuong phap Udc lUOng dung trong nghien nay la SUR (Seemingly Unrelated Regression) de dat dupc tinh hidu qua va bao ham kha nang cd tUdng quan dong thdi glQa cac sai sd ng^u nhien trong he thd'ng cae phUdng trinh cau, vi dieu kien cdng ddn tao ra mot ma tran hiep phUdng sai khac thudng. Do vay, mdt phuong trinh nao dd phai dupc loai bd tu he thdng ham cau trude khi udc lapng (trong nghien cCiu nay phupng trinh ham cau cho mat hang ca dupc loai bd). Cae rang budc cdng ddn td (3) dupc sd dung de tim cac tham sd
De tinh he so co dan trong mo hinh ham cau Hicksian chtjng ta sd dung phuong trinh Slutsky nhU sau.
;* = /:„ + « ,.-), (Eij" do CO dan Hicksian, Ely do co dan Marshaltian) KHOA HOC
16 Tliiitfng n/lai' So 49/2012
HUSH 1^' T A qjuhi I X
trong phudng trinh ham cau cho mat hang ca bi loai bd. Cac he s d co dan cua cau theo chi lieu (thu nhap), theo gia neng va theo gia cheo dUpc tinh theo cac cdng thQc (6), (7) va (8). Tnang nghien cQu nay, cac hd s d eo dan deu dupc tinh tai diem trung binh mail.
DOIi$u nghien cOu va kyihu$t udc lapng mo hinh DQ lieu cho nghien cUu nay la dO iieu thU cap.
loai dO lldu cheo dupc thu thap tQ cudc dieu tra ve mQc sdng cua hd gia dinh d Viet Nam (VHLSS2008). Tac gia sd dung ma'u "thu nhap va chi tidu" gdm 9.189 hd gia dinh trong cupc khao sat de phan tich vi d day cd day du dQ lldu ve tat ca c^c bien can thiet cho yeu cau cua nghien cQu nay. DQliau dUpc thu thap 2 nam mdt l i n do Tdng cue Thdng ke thue hien.
D d Udc lupng hS sd co dan cua cSu theo thu nhap (ehi tieu), dQ lidu vi md d mQc dd hd gia dinh la thich hpp hPn. vl cd the tranh dupc van de cdng gijp cac hang hda khi udc lUpng. Tuy nhien, viec sd dung dO li&u hd gia dinh cho muc dich ude lapng nhieu loai m§t hang rieng le cd the dan tdi mpt van de khd khan khi udc lupng do mdt so hd gia dinh cd mdc tieu dung bang 0 (khdng mua) Van de nay bat ngudn td thuc te rang mdt sd hd khdng tieu dQng mdt sd loai m5t hang nhat dmh trong suot thdi gian khao sat. Trong 4 mat hang thit va ca cua nghien cQu nay, van de tieu dung bSng 0 dSc bldt nghiem trpng doi vdi hai mat hang la thjt bd va thit ga vdi ty le hd gia dinh khdng mua thit bd va thit ga lan iQpt Id 40,94% va 53,38%
(tinh toan cua tac gia tQ bd dQ lieu VHLSS2008).
Cac nghien cQu trudc chi ra rang, neu chung ta chi sd dung dO li#u tieu dung dapc quan sat cd gia tri dUPng de udc lapng hanh vi tieu dung bang phaong phap binh phUdng be nhat thdng thudng (OLS) se cho ket qua la cac udc lupng OLS bi Chech va khdng nhat quan do va'n de thien lech trong chon mau. vl vay lam giam kha nang du bao cua md hinh. Bien phu thudc la phan ngan sach dOng cho chi tieu cac loai m3t hang dupc xac dmh eu the (vi dy, mSt hang i nao dd), bang 0 neu hd gia dinh h khdng mua mat hang i va dUdng (+) neu cd mua. Phan chi tieu bang 0 se bi kiem duyet (censored) bdi mot bien tiem an khdng quan sat dUdc. Trong nghien cQu nay, tae gia ap dung md hinh hai budc eua Heckman dd hieu chinh van de tieu dung bang 0 Nghien cdu nay gia thiet rang
tieu dung bang 0 la do van de chpn ma'u, do vay quy trinh hai bUdc cua Heckman se la md hinh phd hpp (Chern & ctg, 2003).
Heckman (1979) da de xuat mdt phuong phap nham giai quyet van de tieu dung bang 0. Ong xay dung md hinh ve quyet dmh tieu dung va sd dyng md hinh hdi quy Probit de xae dinh xac suat mua sam mpt san pham nhat dmh. Cac udc lUPng tU mdhinh hdi quy Probit dupc dung d e t i n h ty le IMR (Inverse Mills Ratio), la ty le cua cac gia tri Udc lupng dUPe eua ham mat dp chuan hda vdi cac gia tn udc lupng dupc cua ham phan phd'i tich luy chuan hda. Ty le IMR dupc tinh cho moi quan sat trong bd dQ lieu, ve mat toan hpc. thu tuc Heckman cd the dUpc md ta nhU sau:
IMR, _^{xP)
(10) (11) (12)
^{xP)
Trong dd. phUPng trinh (10) do ludng bien tiem a'n p*. bien nhi nguyen p cd gia tri bang 1 ne'u p"
> 0 va bang 0 neu p' < 0, x la tap hpp cac bien ddc lap, p la vector tham so thich hop. Trong phUPng trinh (11), q* luu giQ thdng tin ve cac quan sat ed gia tri cua bien nhi nguyen bang 1. Sau khi tinh ty le IMR, phuong trinh Udc lupng cudi cung dUPc phat trien de' bo sung them ty le IMR nham loai bd tinh thien lech chpn mau trong phuong trinh eau va dupc md ta theo ham sau day:
w = f{xp)+X\USL (13)
Trong dd,_/(x|3) la phUdng trinh de Ude lUpng va IMR duoc xem la bien cdng eu. Trong Udc lUpng cudi cung, chi cac quan sat cd gia tn khdng gidi han mdi dupc sd dung. Ty le IMR trd thanh mpt bien ket ndi quyet dmh tham gia (cd tieu dung hay khdng) vdi phUdng trinh ma nd dai dien cho iupng cau. Theo Heckman (1979), thien lech chpn mau xay ra neu tham so X cd y nghTa ve mat thong ke.
Helen va Wesseils (1990) da khai quat quy trinh hai budc cua Heckman de ket hpp ty le IMR cho cae quan sat ed gia tri bang 0 trong bien phu thudc, tu dd sQ dung tat ca cac quan sat trong budc thQ hai. Ty le IMR dUpc tinh cho moi hd gia dinh (h) va hang hda i, sd dung phaong phap adc lupng thich hpp cue dai (maximum likelihood) td
So 49/2012 TiiiAmg n/lai i?
HJGVH TE VA ^AX J7£
md hinh hdi quy Probit va do vay, bang ty le cua ham mat dd chuan tdc ( ^ tren ham phan phdi tich luy chuan tac (O):
IMR,,
va IMR,,,
'0{xl3)
<p{xp) ' \-^{xl3)
Trong dd, x la cac bien giai thich bao gdm cac bien nhan kha'u hpc, logarit gia ca, a la vector tham so thich hpp, va y,^ la bien gia bang 1 neu hd gia dinh h tieu dung hang hda thQ i va bang 0 neu hd gia dinh h khdng tieu dUng. Trong nghien cQu nay, tac gia sCi dyng phien ban da dupc khai quat bdi Heien va Wesseils (1990) tUthu tuc hai bUdc cua Heckman (1979) vi nd bao gdm tat ca cac quan sat trong phUPng trinh hoi quy d bUdc 2. Nhu vay, phuong trinh ham cau dung trong ude lupng cac san pham thit, ca cho khu vuc thanh thi va ndng thdn Viet Nam se dupc phat trie'n nham ket hpp sd hang hieu chinh thien Idch chpn mail (IMR) la:
+ Zr,jln/J;+/^ lnx-£w,[np, +;r,IIVlR,-HL',
tinh ddng nhat va tinh doi xUng dUdc ap dat de dam bao tinh ben vQng ve mat ly thuyet cau. Cac h# so udc lupng cua mat hang ca thu dUPe bSng viec sd dung rang budc cdng don. Ket qua cho thay cac he sd hoi quy cua bien IMR deu cd y nghTa thong ke trong tat ca cae phUdng trinh ham cau thit va ca. Dieu nay ed nghTa la neu ehung ta bd qua van de tieu dung bang 0
BangJ.; Cac tham so Udc lUdng cua md hinh LA/AIDS cho khu vdc ndng thdn
(14)
(15)
Cac bien Intercept Uipi LnP2 Lnpa LnPA Chi lieu (Lnx/P)
IIUR W tnjng binh
Thit Ion 0,9583 (151897)'
-0,0502 (-3,2520)'
-0,0012 (-0,2222) 0,0030 (0,6154) 0,0231 (3,5760)' -0,0687 (-19,9417)'
-0,2743 (-23,0275)'
0,5631 Thit bo -0,1318 (-3,6265)'
-0,0012 (-0,2222)
-0,0156 (-2,0771)'
0,0471 (11,4711)'
0,0090 (3,8623)'
0,0111 (9,2770)' -0,0059 (-2,0700)'
0,0529 Thitqa -0,0029 (-0,1018)
0,0030 (0,6154) 0,0471 (11.4711)'
-0,0585 (-12,5691)'
0,0067 (3,2196)'
-0,0041 (-3,6495)'
0,1015 (39,4600)'
0,0455 Ca 01764
(-)
0,0484
(•)
-0,0303
(-)
0,0084
( • )
-0,0388 {•) 0,0617
(-)
0,1787 0,3385
(-)
(16)
3. Ke't qua nghien cOu va thao lu$n
Ket qua Udc ludng cac tham so cua mo hinh LA/AIDS theo khu vuc thanh thi va nong thon duoc trinh bay 6 bang 1 va 2.
• Ghi chu;
Ty so t d trong ngoac ddn;
dau* chi miic y nghia 1 % . - p i ; gia thjt Idn; p2; gia thit bd;
p3; gia thit ga; p4: gia ca.
Bang 1 va 2 trinh bay ket qua Udc luong cac tham sd cua mo hinh LA/AIDS cho cac mat hang thit, ca d khu vuc ndng thon va thanh th|. Md hinh udc luong vdi
KHOA HOC ^ _ ^ ^ ^ ^ _ _ _ _
18 ThiiUng Mai
,;• Cac tham so udc luang cua mo hinfi LA/AIDS cho khu vuc thanh thj
Thitlqi Thit bo Intercept
Lnpi
1,0675 (13,0777)'
-0,0619 (-2,8143)' LnPz 0,0037
(0,3731) -0,2109 (^.3549)' 0,0037 (0,3731)
Thitqa
Lnpa -0,0130 (-1,3896) -0,0398 (^,3286)'
0,0127 (1.1632)
0,0193 (0.4329) -0.0130
Chi tiSu (Lnx/P) -0.0383 (-6.5572)'
-0.1853 (-11.0024)'
0,0291 (4.5323)'
0.0343 (7.7488)'
0.0291 (4.5323)'
0,4546 0.0083 (2.9968)'
•0,0819 (-19.0976)'
0.0067 (0.8203) 0.0170 _ ( 3 j
0.0968 -0.0083 (-2.7955)'
-0.0870 (-18.2741)'
0.1006 Ca 0.1341
( • )
0.0712 -0.0455
(-)
•0.0228
(-)
-0.0115
i i
0.0383
(-)
0.3542 H 0,3480
So 49/2012
uma^ TM'vk'iaiilifc-tt§
(zero consumption) thi se tdn tai mdt su thien Ideh chpn mau rat manh. Them vac dd, hau het eac tham s d udc luong deu cd y nghTa thdng ke d mdc y nghTa 1 % . cac tham s d Udc luong dupc tU cac phUPng trinh ham eau thit, ca nay dupc sCi dung de tinh cac he sd co dan cua cau theo gia va theo chi tieu (thu nhap) cho tUng khu vuc thanh thi, ndng thdn dong thdi so sanh ket qua giOa chung.
Bang 3.' HP sd'co dan cua cau (MarshalHan) theo gia va theo chi tieu cac mat hang thit va ca cho khu vUc thanh thi va nong thdn
d khu vuc thanh thi cd khuynh hudng tang tieu dung cac mat hang xa xi (thit bd, ca) nhieu hdn so vdi ngudi dan d khu vuc ndng thdn khi tong chi tieu (thu nhap) tang len. Nguoc lai, ngudi dan d khu vue ndng thdn ed khuynh hudng tang tieu dung cae mat hang thdng thudng (thit ipn, thit ga) nhieu hdn so vdi ngudi dan d khu vuc thanh thi khi td'ng chi tieu (thu nhap) tang len.
Cau cho ta't ca cac mat hang thit va ca d khu vuc ndng thdn la CO dan nhieu, trong khi dd, d thanh thi chi cd thit Ipn va ca la CO dan nhieu, cdn thit bd va thit ga lai co dan it. Cac he so co dan cua eac mat hang thit va ca theo gia rieng d khu vuc ndng thdn Idn hPn so vdi khu vue thanh thi, dieu nay ngu y rang cac hd gia dinh d khu vuc ndng thdn nhay cam theo gia Idn hPn so vdi cac ho gia dinh d khu vuc thanh thi. Ket qua nay cung phan anh mUc thu nhap binh quan d khu vUc nong thdn thap Bang 3 trinh bay ket qua tinh toan cae he sd co hdn so vdi khu vuc thanh thi,
dan theo gia va theo chi tieu cac mat Bang 4.' He sd'co dan cua cau (Hicksian) theo gia cac mat hang
M$thang Pi P2 1 Ps 1 P4 chimii(u«P)
Cho khu vifcnonq thai Thit Idn
Thit 1)6 Thitga Ca '
-1.0904 -0.1408 0,1167 0,0403
0,0043 -1,3060 1,0399 4),0992
0,0109 0,8808
•2,2816 0,0165
00823 0,2283 0,1778 -1,1763
0,8780 1,2098 0,9099 1,1823 : Cho khu vuc thanh tij
Thit Idn Thitbd Thjtga Ca
-1,0279 -0,0008 -0,0917 0,1646
0,0163
•0,8771 0,2973
•0,1414 -0,0201 0,2920 -0,9261 -0,0766
-0,0582 0,3697 0,1977 -1,0713
0,9158 , 1,0857 " '•
0,9175 1,1101
I thjt va ca d khu vUc ndng thdn va thanh tht. Ket qua cho thay, cac he so CO dan cua cau theo gia rieng d ca hai khu vuc thanh thi va ndng thdn deu ed dau am (-) va cac he so CO dan theo ehi tieu (thu nhap) cd dau dUPng (+), dieu nay !a phu hpp vdi cae ky vong ly thuyet. Bdi vdi ca hai khu vuc ndng thdn va thanh thi, thit Ipn va thit ga la hang hda thdng thudng, trong khi dd thit bd va ca lai la hang hda xa xi. He sd co dan theo chl tidu (thu nhap) cua thit Ipn va thit ga d khu vuc ndng thdn nhd hon so vdi khu vuc thanh thi, nhung hd so co dan theo chi tieu (thu nhap) cua thit bd va ca d khu vUc thanh thi lai cao hOn so vdi khu vuc ndng thdn. Ket qua nay cd nghTa la ngUdi dan
thit va ca cho kha vac thanh thi va nPng thdn
IV^thang Pi 1 P2 1 Pa P4
Cho khu vUc nong then Thit Ion
Thit bb Thit ga Ca
-0,5260 0,5404 0,6290 0,7061
0,0508 -1,2420 1,0881 -0,0366
0,0508 0,9359 -2,2402 0,0703
0,3795 0,6378 0,4858 -0,7761 Cho khu vut thanh thi
Thit Ich Thit bo Thit ga Ca
-0,6816 0,4928 0,3254 0,6592
0,1049 -0,7720 0,3861 -0,0339
0,0720 0,4012 -0,8328 0,0351
0,2605 0,7475 05170 -0,6850 Bang 4 trinh bay ket qua tfnh toan cac he sd co dan cua cau (Hicksian) theo gia rieng va theo gia
So 49/2012
-JCHOA HOC ^
ThiAmg n/lai n
l i l X I l TE VA QUAIIir O
cheo cho cac mat hang thit va ca d khu v^c thanh thi va ndng thdn. Ket qua cho thay, tat ea eac he sd CO dan cua cau theo gia rieng deu cd dau am (-) cho ca khu vuc thanh thi va ndng thdn. Dieu nay la hoan toan phu hpp vdi cac ky vpng ly thuyet ban dau. Hd sd co dan theo gia rieng cua thit bd va thjt ga d khu vuc ndng thdn la Idn hdn 1, cd nghTa la cac hd gia dinh d khu vuc ndng thdn rat nhay cam vdi su thay dd'i ve gia eua hai mat hang thjt bd va thit ga, trong khi dd thrt Ipn va ca lai ft co dan theo gia. Ci khu vuc thanh thi, tat ca cac m§t hang thit va ca deu cd he so co dan theo gia rieng nhd hon 1, cd nghTa la cac hd gia dinh 6 khu vpc thanh thi it nhay cam theo gia ddi vdi cac mat hang thit va ca. Ket qua nghien cdu cung chi ra thit bd, thjt ga vd ca la nhOng mat hang thay the eho thit Ipn d ca khu vuc thanh thi va ndng thdn.
Ket lu#n
Bai bao da tien hanh mdt phan tich thuc nghidm v i nhu cau tieu dung cac san pham thit va ca d khu vuc thanh thi va ndng thdn Vidt Nam.
IVluc dich cua nghien edu nay la udc lupng hd so eo dan cua cau cho thit bd, th|t Ipn, thit ga va ea.
C^c h$ so eo dan nay cd the duoc sd dung cho cac phan tfch chinh sach d Viet Nam, Ket qua phan tfch chi ra rang, cau cho tat ca cac mat hang thit va ca d khu vuc ndng thdn la co dan nhieu, trong khi dd, d thanh th| chi ed thit Ipn va ca la co dan nhidu, cdn thit bd va thit ga lai co dan it.
Nghien cdu cung cho thay eac hd gia dinh d khu vuc ndng thdn nhay cam ve gia hdn so vdi nhOng hd gia dinh d khu vuc thanh thk Doi vdi ca hai khu vyc thi thit tpn va thit ga la hang hda thdng thudng, trong khi dd thjt bd va ca lai la hang hda xa x i . *
Tai liiu iham khao:
1. Benjamin, D. and L. Brandt, Agriculture and Income Distribution in Rural Vietnam under Economic Reform: A Tale of Two Regions. William Davidson Working Paper, No.519/03, 2002.
2. Deaton A. S. and J. Muellbauer. Economics and Consumer Behavior, Cambridge University Press, Cambridge, 1980.
3. Haughton, J., L.T., Due, N.N,, Binh, and J.
Fetzer, The Effects of Rice Policy on Food Self- SufTiciency and on Income Distribution in Vietnam, Working Papers, Ford Foundation & General Statistics Office Project. Vietnam, 2004.
4. Heckman, J.J., Sample selection bias as a spec- ification en-or, Econometrica, 47,153 -162,1979.
5. Heien, D. & Wesseils, C.R., Demand system estimation with microdata: A censored regression approach. Journal of Business and Economic Statistics, 8, 365-371, 1990.
6. Linh Vu Hoang, Estimation of Food Demand from Household Survey Data in Vietnam, Working Paper Series No. 2009/12. DEPOCEN WORKING PAPERS are available online at http://www.depocenwp.org.
Summary
The article presents the findings of a survey on the demand for fish and meat of consumers in Vietnam urban and rural areas via the use of AIDS model (Almost Ideal Demand System). The sun/ey uses secondary data collected from a survey on living standards of Vietnamese households con- ducted in 2008 by the General Statistics. The cen- sored regression for equations is applied The two-step demand equations are estimated. In the first phase, the Inverse Mill Ratio (IMR) is estimat- ed by using profit regression model. In the second phase, IMR estimated in the first phase is added to AIDS to estimate the elasticity of demand for fish and meat. The survey aims at estimating the elasticity of demand for various kinds of meat and fish in the urban and rural areas of Vietnam. The indicators of the estimation models are used to calculate the demand elasticity according to Hicksian and Marshallian prices and the demand elasticity according to consumption. The findings show that the elasticity according to spending (income) for pork and chicken in the rural is tower than that in the urban areas but the elasticity according to spending (income) for beef and fish in the urban is higher than that in the rural areas.
In both areas, pork and chicken are the two ordi- nary stuff while beef and fish are considered luxu- ry items.
KHOA HOC
