Improvements Of Sample Design For Rural Statistical Surveys In China

1. 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

2. Chinese Census of Agriculture • First National Agricultural Census --- 1996 • 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

3. 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.

4. 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 1996 --- NBS and the National Agricultural Statistics Service (NASS) of the U.S. Department of Agriculture --- cooperative agreement.

5. Chinese Survey Program • Household Survey – farmers income and expenditures – since 1954 • Crop Yield Survey – since 1963 • 857 Sample Counties Were Selected – 1984 • Three types of surveys implemented: * Farmers Household Survey * Crop Yield Survey * Socio-economic Survey

6. RSO Plan For Survey Expansion • RSO decided to expand survey program in 1999. • 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

7. 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

12. Census Data Useful For Analysis

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

19. 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.

20. Alternative 3 • Select villages with the current sample of counties.

22. Comparison of Sample Design StrategiesRatio of RMSEs (root mean square errors)

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

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

26. Stratified Design ProblemTwo Commodities – Three Size Groupings

27. MPPS

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

29. 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.

30. Determining Probability of Selection for MPPS Design • Probability = Max (PPS1, PPS2, ...,PPSK) • (for 1 to k commodities) • Sample Weight = 1 / Probability

31. Determining Probabilities of Selection for MPPS • Probability = ) ( Farm control 1 Farm control K ,..., Max n1 * nK * Total for State 1 Total for State K (for 1 to K commodities)

32. 1. Select a GENERAL sample with n=5 for cropland and n=5 for capacity Record Control Control Relative Relative Probability Probability Max Prob Random In Exp Number Data Data Measure Measure of of of Number Sample Factor Cropland Capacity Col 2 / Col 3 / Selection Selection Selection = 1 1 / col 8 (000) 10000 10000 Col 4 *n Col 5 *n Max(6,7) (1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) 1 2000 1200 0.200 0.120 1.000 0.600 1.000 0.1603 1 1.000 2 1800 800 0.180 0.080 0.900 0.400 0.900 0.9856 3 1500 700 0.150 0.070 0.750 0.350 0.750 0.2247 1 1.333 4 1400 600 0.140 0.060 0.700 0.300 0.700 0.4889 1 1.429 5 800 700 0.080 0.070 0.400 0.350 0.400 0.0972 1 2.500 6 600 300 0.060 0.030 0.300 0.150 0.300 0.8641 7 500 0.050 0.000 0.250 0.000 0.250 0.7299 8 400 500 0.040 0.050 0.200 0.250 0.250 0.9874 9 300 0.030 0.000 0.150 0.000 0.150 0.1318 1 6.667 10 250 150 0.025 0.015 0.125 0.075 0.125 0.1530 11 200 100 0.020 0.010 0.100 0.050 0.100 0.2952 12 100 0.010 0.000 0.050 0.000 0.050 0.3829 13 60 100 0.006 0.010 0.030 0.050 0.050 0.2283 14 50 50 0.005 0.005 0.025 0.025 0.025 0.4382 15 30 0.003 0.000 0.015 0.000 0.015 0.6579 16 10 0.001 0.000 0.005 0.000 0.005 0.2825 17 1800 0.000 0.180 0.000 0.900 0.900 0.2366 1 1.111 18 1500 0.000 0.150 0.000 0.750 0.750 0.8459 19 1000 0.000 0.100 0.000 0.500 0.500 0.0659 1 2.000 20 500 0.000 0.050 0.000 0.250 0.250 0.9685 Total 10000 10000 1 1 5 5 7.47 7 16.040 Sampling Exercise: Multivariate Probability Proportional to Size (MPPS)

35. 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

36. Part A --- 1000 Villages • Part B --- 2000 Villages • Part C --- 3000 Villages Sample Sizes

37. Sample Options (1) Part A ---- 1000 Villages (2) Parts A and B ---- (1000 + 2000) 3000 Villages • (3) Parts A, B and C --- (1000 + 2000 + 3000) • 6000 Villages

38. Sample SizesSample of Villages – Three Levels Of GovernmentHigh Priority Items

39. Sample SizesSample of Villages – Three Levels Of GovernmentMedium Priority Items

40. Sample SizesSample of Villages – Three Levels Of GovernmentSpecialty Items

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

42. Guangdong Province Pilot Surveys • First pilot survey conducted in 2000 --- 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 2002. • Beginning in 2002, Households were sampled in selected villages.

43. Guangdong Province Survey - 2003

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