About two-thirds of United States senators were millionaires in 2008, according to a recent analysis of politicians’ fortunes conducted by the Center for Responsive Politics.

The research organization, which also tracks political donations, recently analyzed the assets and liabilities of lawmakers based on 2008’s required annual financial disclosures. The center estimated each politician’s net worth by adding together the lawmaker’s range of assets and then subtracted the range of liabilities.

The midpoint of that resulting range was used to rank the politicians.

In the Senate, 68 legislators were estimated to be worth at least $1 million, led by Herb Kohl, a Democrat from Wisconsin, who was worth an estimated $214,570,011 in 2008. The average net worth across the Senate was $13,989,022.98.

Here is the center’s list of the 25 wealthiest senators from 2008:

Source: Center for Responsive Politics

In the House, 240 legislators were worth at least $1 million. The richest representative was likely Darrell Issa, a Republican from California, who was worth an estimated $251,025,020 in 2008. The average net worth across the House was $4,670,831.

Here is the center’s list of the 25 wealthiest representatives from 2008:

Source: Center for Responsive Politics

The center’s site is missing a few entries (and since the data are from 2008, not all of the numbers are still relevant for the current Capitol Hill crowd; the late Senator Edward M. Kennedy is included, for example). But the site contains a wealth of useful information on legislators’ assets nonetheless.

This chart, for example, shows the most popular investments among legislators, with General Electric and Bank of America topping the list.