Appendix F: Physical Functioning Models

From Planning for the Future
p. 97-100, published 2002

Model Specification

The estimated likelihoods shown on page 36 are based on the relationship between limitations in physical functioning and gender, age, race, ethnicity, marital status, education, income and location of residence in an urban or rural area. We use probit models to estimate the relationship between limitations in six categories of physical functioning and these socioeconomic and demographic characteristics. Six dependent variables equal 1 if a person has been limited for greater than three months or less than three months and 0 if the person is not limited at all in each of the six categories of physical functions described. To see the actual question used to generate these variables please refer to Appendix A, question 34. The six different categories of physical functioning range from the most vigorous activities such as running, lifting heavy objects, or participating in strenuous sports to the most basic activities of eating, dressing, bathing, or using the toilet. These are the only two categories of physical functioning shown in the figure on page 36. The independent variables in the model are listed below, along with parameter estimates in Table F.1:

The next stage of this analysis involved comparing two groups from our sample––the retired respondents and the nonretired respondents. To do this we estimated the means for each of these two groups for all the independent variables used in the models, except age. Table F.1 lists the means for the two different groups. The nonretired group has higher incomes, as expected, but also higher educational attainment levels, on average. These two characteristics have been shown repeatedly by researchers to affect health outcomes significantly. These means were used to estimate the likelihood the “typical” retiree would be limited in each of the physical functioning categories at each age compared to the likelihood the “typical” nonretiree would be limited at each age. Although not shown here, for each of the categories analyzed, the likelihood that a retiree would be limited was greater at each age than the likelihood of a nonretired Kentuckian regardless of the physical functioning category. As can be seen in Table F.1, many of the same independent variables, namely education and income, are statistically significant and have the same signs in the other four categories of physical functioning as in the two shown in the text. These results suggest that we may see better health statuses in the area of physical functioning among coming retirees in their later years than those that are typical of current Kentucky retirees.

Table F1:  Means of Demographic Characteristics for Workers and Retired Kentuckians and Parameter Estimates of the Likelihood of Limitations in Six Categories of Physical Functioning of Kentucky’s Aging Population, 2000

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