It is an interesting but misleading statistic: The total net worth of Congress rose by about 25 percent during the past two years, but the net worth of female Members of Congress declined by more than 20 percent over the same period.

Blame Jane Harman.

The California Democrat was one of the wealthiest Members of Congress for years before retiring from the House earlier this year and taking her net worth of more than $100 million with her. With Harman gone, the total minimum net worth of women currently in Congress is about $247 million, down from $319 million two years ago.

Harman’s case demonstrates how a few exceptionally wealthy Members of Congress can skew the wealth curve in a body that has only 541 members.

In the wake of Roll Call’s report last week that the minimum net worth of Congress had jumped about 25 percent in two years, several people asked about the gender breakdown of Congressional wealth. How much of it is women?

Roll Call reanalyzed the data by gender and came up with a bunch of interesting but contradictory conclusions.

The data come from annual financial disclosure forms filed by Members each May covering the prior calendar year, so this year’s figures actually cover the wealth of current Members as of Dec. 31, 2010.

For starters, the overwhelming majority of the money in Congress is held by men — about $1.8 billion out of the $2.04 billion minimum total reported on the forms.

But of course, just because a male Member of Congress, such as Sen. John Kerry (D-Mass.) or Rep. Michael McCaul (R-Texas), reports a net worth of more than $200 million doesn’t mean that money belongs to the man. McCaul and Kerry come to their fortunes through marriage. The money mostly belongs to the Members’ wives.

Still, the same could be said of Harman and other super-rich women in Congress, such as Sen. Dianne Feinstein and House Minority Leader Nancy Pelosi. The California Democrats report a personal net worth in the tens of millions of dollars, and for the most part, the assets are listed in their husbands’ names.

So ignoring the source of wealth, a straight male-vs.-female comparison of Members of Congress shows that male Members of Congress have an average minimum net worth of about $4 million and female Members have an average of about $2.7 million.

But wait — the lion’s share of all assets in Congress are controlled by a few of the very wealthiest Members, and nine of the top 10 richest are men. So instead of averaging that massive wealth across the whole Capitol, it makes more sense to find the midpoint of wealth for each gender. And here the narrative flips.

Among the 93 female Members of the 112th Congress, the midpoint of net worth is about $650,000. Half of the women are above that number, half are below.

For the 448 men, the median net worth is about $490,000.

And in those numbers, there is a kind of equality — for men and women in Congress, the median net worth rose about 13 percent during the two-year period.

Roll Call calculates minimum net worth by adding the minimum values of all reported assets and subtracting the minimum values of all reported liabilities on the forms Members submit each year.

In general, the wealth totals vastly underestimate the actual net worth of Members of Congress because they are based on an accounting system that does not include homes and other non-income-generating property, which could tally hundreds of millions of uncounted dollars.

In addition, Roll Call’s count is based on the minimum values of assets reported by Members on their annual financial disclosure forms; the true values of those assets might be much higher.