Table 2.

The results of generalized estimating equations regression model (USD/year).

	Estimate	SE	P value
Intercept	33.4	1.5	<0.001
Age, year (versus <40)
40–64	10.4	1.4	<0.001
≥65	18.5	1.5	<0.001
Gender (versus female)	2.2	1.1	0.041
Income, USD (versus ≤610)
611–1220	−3.2	1.3	0.015
>1220	6.7	2.0	<0.001
Occupation (versus white-collar workers)
Blue-collar workers	−6.7	1.3	<0.001
Other types of workers	6.8	1.6	<0.001
Year	1.0	0.1	<0.001