One of the measures used in studying health and obesity is the Body Mass Index (BMI). A BMI measure between 20 and 25 is considered healthy; a measure of over 30 makes a person obese. The average BMI in the United States rose from 25 to about 27.75 in the last 25 years. This is considered a large increase, and many social scientists have been trying to explain this trend. The results below come from a regression estimated using a national cross section sample of adults. The dependent variable was BMI, and the sample size was over 42000.
|
Independent Variable
|
Sample Mean of Variable
(Standard Deviation)
|
Coefficient in Regression
(Standard Error)
|
|
Restaurants per capita in respondent's state
|
11.04
(2.27)
|
.473
(.324)
|
|
Age in years
|
41.24
(16.68)
|
.326
(.016)
|
|
Age squared
|
--
|
-.003
(.0002)
|
|
Cigarette tax per pack in cents in respondent's state
|
22.58
(9.77)
|
.058
(.032)
|
|
Cigarette tax squared
|
--
|
-.001
(.0004)
|
|
Household income in 10,000s of dollars
|
2.91
(2.39)
|
-.393
(.168)
|
a. According to this regression, at about what age does BMI reach its highest level in American adults, other things equal?