<p>Here's some data on revealed preferences. I know it's just a statistic, but these were the results of the New York Times study last year:
<a href="http://www.nytimes.com/imagepages/2006/09/17/weekinreview/20060917_LEONHARDT_CHART.html%5B/url%5D">http://www.nytimes.com/imagepages/2006/09/17/weekinreview/20060917_LEONHARDT_CHART.html</a></p>