I've almost always seen class in America to be based on income. It seems useful to publish results that define class by income; it is commonly understood to be

I've almost always seen class in America to be based on income. It seems useful to publish results that define class by income; it is commonly understood to be income; income may not have as much a correlation with power and quality of life as capital as you suggest, but i preaume that it is still large. Finally, the deciding reason to measure income class is the probable assumption that it is far easier and far more accurate to obtain estimates on the income of US citizens than on their net worth.