Max Rady College of Medicine
Concept: Household Income: Individual versus Census Area
Last Updated: 2006-03-15
The relationship between individual household income and the mean (or median) household income as defined using the smallest possible census areas is an issue which frequently comes up. Individual household income is not typically available in administrative data files and yet researchers wish to use household income, a variable shown to be important in many analyses (often using survey data).
This problem has been approached in two ways:
by presenting the relationship between individual and census area categories of income.
The following table compares actual household income quintile (from the census) with MCHP small area income quintiles calculated from the 1986 census linked sample, including only Winnipeg residents (N=22185). The sample is described in Mustard et al. (1999) . The MCHP macro is based on postal codes. The following table displays the agreement on urban quintile rank (the percentages sum to 100% within MCHP ranks).
Household Income Rank (from Census) U1 U2 U3 U4 U5
U1 45.5% 24.8% 19.6% 11.1% 5.8%
U2 23.8 27.8 24.1 18.5 10.2
U3 16.4 21.6 21.5 22.1 17.7
U4 9.1 15.2 19.4 26.7 25.1
U5 5.2 10.7 15.4 21.7 41.2
Spearman correlation coefficient 0.435
Exact match on quintile 190226
Percent matching exactly 32.8%
Matching within one quintile
(includes exact match)
398139 Percent within one quintile 68.7%
by using ecologic-level measures of income as proxies for individual-level measures
Mustard et al. (1999) examine the effectiveness of using ecologic measures of income in predicting differences in population health when individual-level measures of income are unavailable. The study is based on a representative sample of 5% of the Manitoba population in 1986 (N=47,935). From the combination of information from administrative records of individual health care use, records of death, and 1986 census records containing information on household income and average neighborhood income, thirteen measures of health status were developed. The results from the study suggest that risk estimates from ecologic income measures are not weakened relative to estimates obtained from household income and provide evidence for the use of ecologic-level measures of income as proxies for individual-level measures (Mustard et al. (1999) ).
This area is a controversial one, with studies conflicting as to the extent to which aggregate data provide a reasonable approximation of individual-level data. A list of studies (and a differing point of view) is provided by
Southern et al. (2005)
Differences among studies may be due to:
the accuracy with which neighborhood is assigned to individuals
- the cutting points used to assign individuals to categories. Ideally, categories used (quintiles, for example) should contain the same number of individuals in each category.
- Mustard CA, Derksen S, Berthelot JM, Wolfson M. Assessing ecologic proxies for household income: a comparison of household and neighbourhood level income measures in the study of population health status. Health Place 1999;5(2):157-171. [Abstract] (View)
- Roos NP, Mustard CA. Variation in health and health care use by socioeconomic status in Winnipeg, Canada: does the system work well? Yes and no. Milbank Q 1997;75(1):89-111. [Abstract] (View)
- Southern DA, McLaren L, Hawe P, Knudtson ML, Ghali WA. Individual-level and neighborhood-level income measures: agreement and association with outcomes in a cardiac disease cohort. Med Care 2005;43(11):1116-1122. [Abstract] (View)
- socioeconomic status
Manitoba Centre for Health Policy
Community Health Sciences, Max Rady College of Medicine,
Rady Faculty of Health Sciences,
Room 408-727 McDermot Ave.
University of Manitoba
Winnipeg, MB R3E 3P5 Canada