As a result of the FRB's review of the 2003 SSBF data, fourteen cases that completed the main interview were found ineligible for the survey because they were majority owned by other business firms instead of individuals and fourteen cases were found to be ineligible due to out of scope industry activity. The 28 ineligible cases and their corresponding size class, urban/rural status, and original final weights are shown in Table 1. As a result, these twenty eight cases were dropped from the sample (reducing the sample from 4268 to 4240) and the sample weights recalculated. The reweighting had a minimal effect on response rates, effective sample sizes, design effects, weight variances, or estimated population and subpopulation totals. This document describes the weighting adjustments, provides some comparisons, and updates the weighting information from the 2003 SSBF Methodology report.1
The reweighting process involved rerunning all weighting programs following the final screener weighting program (wt8ih-wt10ih). It was not necessary to reweight anything prior to the main interview as there was already an established protocol in place to screen out ineligible firms at the main interview. The 28 additional ineligible cases were assigned a main weight (wt8ih) of zero, exactly like the cases that were identified as ineligible during the main interview; eligibility-adjusted and trimmed final weights were then recalculated for the remaining 4240 cases. After calculating the pre-trim weight (w9tih), design effects and pre-trim weights were analyzed in order to determine if there was any need for weight trimming. It was determined that it would be beneficial to keep the original number of cases trimmed in size class 0-19 (0 cases), class 20-49 (4 cases), and class 100-499 (10 cases) but three additional cases were trimmed in size class 50-99 (15 cases). By trimming three additional cases, the design effect for size class 50-99 was brought down to just a little over 2.0. Outlier weights were trimmed to the largest non-outlier weight in the size class (maximum values in Table 5). Last, the summary program was rerun and new response rates, design effects, effective sample sizes, population totals and subtotals were calculated.
There were minor changes in the response propensities, nonresponse cell assignment, and the nonresponse adjustment, although these changes had little impact on the final estimates. The response propensities changed for each case because the total number of pre- and post- reweighted complete and incomplete cases differed. Therefore, when the data was run through the original logistic regression model, each case had a slightly different response propensity score. The changes in propensity score per case caused the average propensity per nonresponse adjustment cell to change as well.
Table 2 shows the similarity in the average propensity score within the pre- and post-reweighted nonresponse adjustment cells. After calculating the response propensities for each case, the cases were sorted by ascending response propensity score within size class. Because some of the response propensities changed, the sort order did not remain the same, changing the composition of nonresponse cells slightly. This in turn gave a slightly different response rate within each nonresponse adjustment cell. The change in the response rate within each nonresponse adjustment cell led to slightly different nonresponse adjustments and nonresponse adjusted weights (wt10ih).
Tables 3-9 below compare the weights, response rates, design effect, effective sample sizes and population totals before and after reweighting. We also compare population estimates (see Table 10) before and after reweighting for three key analysis variables: average total employment, average sales, and the distribution of firms by organizational form.
Reweighting had little impact. As shown in Table 3, the main (52%) and the overall (32%) response rates were virtually unchanged. Tables 3-7 provide updated estimates of the design effects and effective sample size by size class and urban/rural status. The design effects for the first two size classes remained similar and there was a slight reduction in the design effect for the two largest size classes. Table 8 shows the total number of firms in the universe prior to reweighting was 6,333,780 compared to post reweighting total of 6,298,088. The loss of 35,692 firms consists of the 15,898 firms represented by the twenty eight affected cases as well as 19,794 additional firms generated by the increased predicted ineligibility rate among the incompletes.2 Table 9 shows the similarity between the pre-reweighted and post-reweighted total number of firms by size class and urban rural status.
Table 10 shows the effect the reweighting had on the three key analysis variables: organizational type, employment, and sales. The reweighting had a negligible effect on the total number of employees, the total sales volume, the average number of employees, the average sales volume, the median number of employees, the median sales volume and the percentage of firms by organizational type.
The reweighting proved to have little impact on the final weights and estimates. The estimated number of firms in the target population fell somewhat, as was expected. Although there was little impact on the final estimates, this exercise proved necessary to correct inaccurate information contained in the 2003 SSBF Methodology Report.
|Obs||SU_ID||Size class||Urban/Rural||Original Final
|Nonresponse Adjustment Cell||Size Class||Sample Size||Mean Response Propensity
|Mean Response Propensity
|Diff in mean Response Propensity|
|Interview Type||Response rate based on Old Weight||Response rate based on new weight||DEFF based on old weight||DEFF based on new weight|
|Size Class||Count||Max||Mean||St Dev||CV||DEFF||Effective sample size|
|Size Class||Count||Max||Mean||St Dev||CV||DEFF||Effective sample
|Count||Max||Mean||St Dev||CV||DEFF||Effective sample size|
|Size Class||Old Weight
Weighted Total of firms
Weighted Total of firms
Weighted Total of Firms
Weighted Total of Firms
|Type||Old Weight (4240)||New Weight
|Total Firms in the Universe||N/A||6,302,811||6,298,088|
|Percentage of firms by Organizational Type (B3)||Corporations||15.70||15.69|
|Percentage of firms by Organizational Type (B3)||Partnerships||8.61||8.65|
|Percentage of firms by Organizational Type (B3)||S-corporations||31.09||31.07|
|Percentage of firms by Organizational Type (B3)||Sole Proprietorship||44.59||44.59|