Improvements Of Sample Design For Rural Statistical Surveys In China Michael Steiner National Agricultural Statistics Service United States Department of Agriculture Xian Zude Rural Survey Organization Chinese National Bureau of Statistics

Chinese Census of Agriculture First National Agricultural Census Census Questionnaires – 38 sections, 687 data items Data collection – January 1997 Data collected for approximately 214,000,000 rural households Approximately 7,000,000 interviewers were utilized for data collection

Use of Chinese Census Data Provides a wealth of crop, livestock and rural household statistics. Provides estimates of small administrative units. Provides estimates of rare commodities. Provides data for a sampling frame.

Chinese Agriculture Statistics National Bureau of Statistics (NBS) of PR China Food and Agricultural Statistics Centre (FASC) of NBS --- Chinese Census of Agriculture Rural Survey Organization (RSO) --- Agricultural & Rural Statistics for China – established in 1984 Since NBS and the National Agricultural Statistics Service (NASS) of the U.S. Department of Agriculture --- cooperative agreement.

Chinese Survey Program Household Survey – farmers income and expenditures – since 1954 Crop Yield Survey – since Sample Counties Were Selected – 1984 Three types of surveys implemented: * Farmers Household Survey * Crop Yield Survey * Socio-economic Survey

RSO Plan For Survey Expansion RSO decided to expand survey program in Expanded survey program to cover: * Crop Area for Major Crops * All Major Types of Livestock (Inventory and Slaughter) * Agricultural Prices and Costs * Poverty Measurement Complete Reporting System

Guangdong Province Pilot Survey Work Project Involving Guangdong Bureau of Statistics, NBS-RSO, and USDA-NASS Guangdong Province designated as site for pilot survey work. Guangdong Province: * 21 Prefectures * 122 Counties * 23,870 Villages

Census Data Useful For Analysis Sampling Alternatives

Alternative 1 Select samples from villages within all counties in a province.

Alternative 2 Select villages within a NEW sample of counties. Continue the practice of having samples only in selected counties (not all counties). Select a new sample of counties and replace the old sample of counties.

Alternative 3 Select villages with the current sample of counties.

Comparison of Sample Design Strategies Ratio of RMSEs (root mean square errors) Stages of Sampling Total Area Sown Total Area for Grain Total Area for Rice All Counties, Villages 111 New Counties, Villages Old Counties, Villages

Methods of Sampling

Stratified Sampling ***Census Data Available For Stratification*** Disadvantages: Becomes difficult to create efficient stratified design when number of variables of interest increases.

Possible Commodities For Sample Selection Land in Grain Wheat Rice Corn Tuber Crops Rapeseed Peanuts Vegetables Orchard Area Pond Area Cattle Sheep Hogs Poultry

Stratified Design Problem Two Commodities – Three Size Groupings Items Rice Area (Large) Rice Area (Medium) Rice Area (Small) Hog Inventory – Large L L ML S Hog Inventory -Medium M LM M S Hog Inventory - Small S LS MS

MPPS Methods of Sampling

MPPS Sampling Multivariate Probability Proportional to Size: Probability proportional to size sample design in which the measure of size is determined by more than one variable.

Probability Proportional to Size (PPS) Sampling A sample is said to be chosen with probability proportional to size if the probability of selection for each unit in the population is proportional to some measure of the size of the unit.

Determining Probability of Selection for MPPS Design Probability = Max (PPS 1, PPS 2,...,PPS K ) (for 1 to k commodities) Sample Weight = 1 / Probability

Determining Probabilities of Selection for MPPS Probability = Total for State 1 ( Farm control 1 Max,..., Farm control K Total for State K ) n 1 * n K * (for 1 to K commodities)

1. Select a GENERAL sample with n=5 for cropland and n=5 for capacity RecordControl Relative Probabilit y Max ProbRandomInExp NumberData Measure of NumberSampleFactor CroplandCapacityCol 2 /Col 3 /Selection = 11 / col 8 (000)10000 Col 4 *nCol 5 *nMax(6,7) (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11) Total Sampling Exercise: Multivariate Probability Proportional to Size (MPPS)

Sample Sizes – MPPS Design Separate samples were selected in order to accommodate different levels of government Part A --- Funded by Provincial Government Part B --- Funded by Prefecture Governments Part C --- Funded by County Governments

Sample Sizes Part A Villages Part B Villages Part C Villages

Sample Options (1) Part A Villages (2) Parts A and B ---- ( ) 3000 Villages (3) Parts A, B and C --- ( ) 6000 Villages

Sample Sizes Sample of Villages – Three Levels Of Government High Priority Items ItemsProvincePrefectureCounty Grain Area Vegetables Hogs Poultry

Sample Sizes Sample of Villages – Three Levels Of Government Medium Priority Items ItemsProvincePrefectureCounty Tuber Crops Orchards Cattle250258

Sample Sizes Sample of Villages – Three Levels Of Government Specialty Items ItemsProvincePrefectureCounty Pond Area Peanuts15055

Sample Selection Procedure First Stage: Selection of villages (Using MPPS) Second Stage: Selection of Households (random stratified) * “Large” Households * Other Households

Guangdong Province Pilot Surveys First pilot survey conducted in villages selected using MPPS in select counties Test survey of villages conducted in three prefectures in 2001, using MPPS for village selection Survey of villages (MPPS sample selection) conducted in entire province in Beginning in 2002, Households were sampled in selected villages.

Guangdong Province Survey CommodityC.V. (%) Grain Area Vegetable Area Tuber Crop Area Orchard Area Peanut Area Hog Inventory Poultry Inventory Net Income Per Capita 4.67

Future Of Agricultural Statistics In China Expansion of MPPS Procedures - Nationwide: Crop Area Planted Survey. Livestock Survey Agricultural Census: 2006