procedures accounted both for nonresponse to the data 

 collection and for the sample data collection. These pro- 

 cedures are used because some farm operators never 

 respond to the census despite numerous attempts to 

 contact them, and not all farm operators are requested to 

 provide the sample data items. 



Whole Farm Nonresponse Estimation 



A statistical estimation procedure was used to account 

 for the census farms among mail list nonrespondents that 

 were not designated for telephone followup. A stratified 

 systematic sample of eligible census nonrespondents were 

 mailed a simplified report form. Five sample strata were 

 defined based on form type, expected value of sales, and 

 previous census status. The report form was designed to 

 provide sufficient information to determine farm status. 

 Additional mail and telephone contacts were made to 

 survey nonrespondents to obtain sufficient response for 

 survey estimates. 



Estimates of the proportion of census nonrespondents 

 that operated farms were made for each stratum in the 

 State using survey results and applied to the total number 

 of census nonrespondents in that stratum. A synthetic 

 estimation procedure was used to estimate the number of 

 census nonrespondents that operated farms for each 

 county by stratum. This estimation procedure is based on 

 the assumption that the distribution of farms in a stratum 

 by county is the same for census nonrespondents as for 

 census respondents. 



Within each stratum in a county, a noninteger nonre- 

 sponse weight was calculated and assigned to each 

 eligible respondent farm record. The procedure used for 

 calculating the nonresponse weight assumed the eligible 

 census respondents and the nonrespondent farm opera- 

 tions in a county had similar characteristics within each 

 stratum. The noninteger nonresponse weight was the ratio 

 of the sum of the estimated number of nonrespondent 

 farms (using nonresponse survey results) and the number 

 of eligible census respondent farms to the number of 

 eligible census respondent farms. Stratum controls were 

 established to ensure that this weight was never greater 

 than 2.0. The noninteger nonresponse weight was used in 

 the estimation of the final weight for the sample items. It 

 was randomly rounded to an integer weight of either 1 or 2 

 for each record for tabulating the complete count items. 



The procedure assumed that we obtain complete response 

 from large and unique farm operations because these 

 cases received intensive telephone followup during cen- 

 sus processing. In situations where addressees could not 

 be contacted by telephone or refused to cooperate, sec- 

 ondary sources such as Agricultural Stabilization and 

 Conservation Service offices or county extension agents 

 were asked to provide information as to whether or not the 

 addressee had agricultural activities. Data from previous 

 census reports for the specific addressee, in conjunction 

 with other information, were used to complete the census 

 report form. 



Tables A and B quantify the effect of the nonresponse 

 estimation procedure on selected census data items. The 

 percentage of the census value contributed by nonre- 

 sponse estimation as provided in these tables indicates 

 the potential for bias in published figures resulting from this 

 procedure. The estimates provided in these tables do not 

 reflect the effect of nonresponse to individual data items 

 on respondents' census report forms. The effect of this 

 item nonresponse is discussed further under Census Non- 

 sampling Error. 



Sampie Estimation 



All respondent sample records received a sample weight 

 The sample data estimates the actual figures that would 

 have resulted from a complete census of the items in 

 sections 23 through 28 of the report form. The estimates 

 were obtained from an iterative ratio estimation procedure 

 that resulted in the assignment of a weight to each record 

 containing sample items. For any given county, a sample 

 item total was estimated by multiplying the data items for 

 each farm in the county by the corresponding sample 

 weight and summing overall sample records in the county. 



Each sample farm was assigned one sample weight to 

 be used to produce estimates for all sample items. For 

 example, if the weight given to a sample farm had the 

 value 5, all sample data items reported by that farm would 

 be multiplied by 5. The weight assigned a certainty farm 

 was 1 . The estimation procedure used to assign weights 

 was performed for each county. 



Within a county, the ratio estimation procedure for farms 

 was performed in three steps using three variables. The 

 first variable contained eight 1 987 total value of agricultural 

 production (TVP) groups. Both the second and third 

 variables. Standard Industrial Classification (SIC) code and 

 farm acreage, contained two groups. The variable groups 

 were as follows: 



I 



TVP 



SIC 



Acres 



$2,500 to $ 4,999 

 $5,000 to $ 9,999 

 $10,000 to $24,999 

 $25,000 to $49,999 

 $50,000 to $99,999 

 $100,000 or more 



The first step in the estimation procedure was to parti- 

 tion the sample records into 32 mutually exclusive initial 

 post strata formed by combining the three variable groups. 

 This produced a three dimensional array where the cells of 

 the array corresponded to the initial post strata groups. 

 Each sample farm record was assigned an initial weight 

 equal to the ratio of the total farm count to the sample farm 



C-2 APPENDIX C 



1987 CENSUS OF AGRICULTURE 



