QUAIDS Model
quaids Command
Usage
Example
代码语言：javascript复制webuse food, clear
/*
First, create a random integer representing the number of children
in each household and a random binary variable representing rural
versus urban households so that we can demonstrate a model that includes demographics.
We then fit a quadratic AIDS model using α0 = 10.
*/
set seed 1
gen nkids = int(runiform()*4)
gen rural = (runiform() > 0.7)
quaids w1-w4, anot(10) prices(p1-p4) expenditure(expfd) ///
demographics(nkids rural) // need to spcify the value for alpha_0
* Wald tests
test [eta]_b[eta_rural_1], notest
test [eta]_b[eta_rural_2], notest accumulate
test [eta]_b[eta_rural_3], notest accumulate
test [eta]_b[eta_rural_4], notest accumulate
test [rho]_b[rho_rural], accumulate
* Compute the expenditure elasticities for each household
estat expenditure e*
summarize e_1-e_4
* Compute the uncompensated prices elasticities for rural and urban households
estat uncompensated if rural, atmeans // atmeans: group-level means
matrix uprural = r(uncompelas)
estat uncompensated if !rural, atmeans
matrix upurban = r(uncompelas)
matrix list uprural
matrix list upurban
/*
Output：
uprural[4,4]
c1 c2 c3 c4
r1 -.71245867 -.13705857 -.09058916 -.09155783
r2 -.18191573 -.71137762 .00549316 -.02571537
r3 -.37992121 -.01990578 -.57693539 -.07470768
r4 -.13712472 -.04801226 -.02494365 -.80164427
. matrix list upurban
upurban[4,4]
c1 c2 c3 c4
r1 -.71465742 -.13979419 -.09222 -.09791097
r2 -.16774212 -.70701879 .00664392 -.0133375
r3 -.33612769 -.01253846 -.5892293 -.05958872
r4 -.1508913 -.05090295 -.02865442 -.81177966
Explanation:
The entry in row i, column j of each elasticity matrix represents the percentage change in the quantity of good i consumed for a 1% change in the price of good j.
每个弹性矩阵的第i行第j列的值表示商品j的价格变化1％时，所消费的商品i数量的百分比变化。
Among rural consumers, a 1% increase in the price of good A raises consumption of good B by 0.33%.
*/References
[1] Poi B P. Easy demand-system estimation with quaids[J]. The Stata Journal, 2012, 12(3): 433-446.
[2] Zheng Z, Henneberry S R, Zhao Y, et al. Predicting the changes in the structure of food demand in China[J]. Agribusiness, 2019, 35(3): 301-328.
[3] 郑志浩, 高颖, 赵殷钰. 收入增长对城镇居民食物消费模式的影响[J]. 经济学 (季刊), 2015, 15(1): 263-288.
[4] 石明明, 江舟, 周小焱. 消费升级还是消费降级[J]. 中国工业经济, 2019 (7): 4.
