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Comparing Global questions and answers to results from detailed specific questions:
Data on Food Expenditures from the Consumer Expenditure Survey, 1998 - 2015
Steven Henderson, 9/20/16
How do the dollar amounts collected from global questions on spending categories compare to answers gathered by specific questions? Are they higher or lower, or similar? Research comparing 18 years of reports of itemized expenditures on food at home and food away from home from the Consumer Expenditure Survey (CE) Diary instrument with the responses from the global food questions from the CE Interview Survey show that it depends. Using detailed prepublication data from 1998 to 2015, the aggregate dollars reported in the Diary for specific food purchases for eating at home are always lower than the global estimates from the Interview. The Diary to Interview ratio for this group of food at home items has consistently ranged between 76 percent and 82 percent.
Conversely, the expenditures reported for eating at restaurants and away from home collected in the Diary are always higher the global estimates from the Interview survey. The range is greater, from 166 percent higher to 189 percent higher between 1998 and 2006, and then from 104 percent to 122 percent higher between 2007 and 2015. There was a change in how the global question in the Interview Survey was asked in 2007 which caused a shift in the ratios.
Results:
Table 1 shows the Diary/Interview ratios for Food at Home, with the amounts adjusted for comparability. See the Methodology section below for how the categories were adjusted. Reported itemized purchases in the Diary are consistently lower than the global estimates from the Interview.
Table 1
Itemized expenditures for Food at Home from the Diary compared to Interview Global Estimates Diary/Interview Ratio
(comparable categories only)
Year | Percent |
---|---|
1998 | 78% |
1999 | 81% |
2000 | 81% |
2001 | 81% |
2002 | 80% |
2003 | 81% |
2004 | 82% |
2005 | 79% |
2006 | 78% |
2007 | 77% |
2008 | 78% |
2009 | 80% |
2010 | 77% |
2011 | 78% |
2012 | 78% |
2013 | 79% |
2014 | 77% |
2015 | 76% |
Table 2 shows the adjusted Diary/Interview ratios for Food away from Home. Respondents in the Diary always report higher spending on itemized meals away from home than the global estimates provided by respondents in the Interview Survey.
Table 2
Itemized expenditures for Food away from Home from the Diary compared to Interview Global Estimates Diary/Interview Ratio (comparable categories only)
Year | Percent |
---|---|
1998 | 166% |
1999 | 172% |
2000 | 169% |
2001 | 185% |
2002 | 189% |
2003 | 178% |
2004 | 185% |
2005 | 192% |
2006 | 189% |
2007 | 104% |
2008 | 121% |
2009 | 122% |
2010 | 117% |
2011 | 121% |
2012 | 116% |
2013 | 117% |
2014 | 116% |
2015 | 119% |
Impact for data users
The results of this comparison are important for researchers who select data from only one survey, rather than using the integrated results from the Diary and Interview that are used in the published CE tables and as cost weights used by the Consumer Price Index. Research work that only uses food expenditures reported in the Interview Survey will undercount the actual amount spent at restaurants, and will overcount the amount spent on food for home consumption. Table 3 shows the ratio of aggregate dollars spent for Food at Home Food Away from the Diary compared to Food at Home + Food Away from the Interview for comparable categories. For the past 9 years the Diary combined amounts have been between 86 and 91 percent of the Interview amounts. The table shows that using the combined global estimates for food from the Interview instead of the reported amounts from the Diary overstates the dollars spent by U.S. households on food. The Interview overcount for groceries is higher than the undercount for restaurant meals, and the differences do not cancel each other out.
Table 3
Itemized expenditures for Food at Home Plus Food Away from Home from the Diary compared to aggregated Interview Global Estimates Diary/Interview Ratio
(comparable categories only)
Year | Percent |
---|---|
1998 | 97% |
1999 | 101% |
2000 | 100% |
2001 | 102% |
2002 | 103% |
2003 | 102% |
2004 | 104% |
2005 | 104% |
2006 | 102% |
2007 | 86% |
2008 | 90% |
2009 | 91% |
2010 | 88% |
2011 | 90% |
2012 | 88% |
2013 | 89% |
2014 | 88% |
2015 | 89% |
Methodology and Data Used
Published total annual food expenditures primarily come from the Diary; however a few expenditures in the integrated total are sourced from the Interview Survey. For the comparisons in this research paper, the only Food at Home expenditure that comes from the Interview — food for home consumption purchased on trips — was subtracted from the total before calculating the ratios. For calculating the Diary-to-Interview ratios for Food away from Home, the amounts for integrated categories that come from the Interview, i.e., board, catered affairs, meals during out of town trips, school lunches, and meals as pay, were subtracted from the total.
Analysis
Why are expenditures for itemized food at home purchases from the Diary always lower than global Interview responses? There are two suggested causes.
Why are itemized food away from home purchases always higher than global estimates? What caused the change in the ratios from 2006 to 2007 in Table 2 and Table 3? There are two key findings.
Last Modified Date: October 11, 2016