Speaker Nancy Pelosi saw her apparent net worth nearly double last year, though much of that could be the effect of the oddities of Congressional disclosure rules.

Other top leaders in the House and Senate also saw their fortunes increase last year, though none as significantly as the Speaker’s.

The California Democrat was already one of the 50 richest Members of Congress, largely based on the strength of her husband’s broad real estate and investment portfolio. In 2008, she had reported assets worth at least $25.2 million. According to her new disclosure report, in 2009 Pelosi’s assets increased to a minimum of $29.7 million, mostly because of the addition of two assets worth $1 million to $5 million – an investment fund specializing in Asian ventures and a United Football League team.

But the minimum value of the Speaker’s liabilities dropped significantly in 2009. In 2008 she had reported a mortgage on a vineyard worth at least $5 million. In 2009, that mortgage was listed as having a value of $1 million to $5 million. For the purposes of Roll Call’s accounting method, that liability is counted as $1 million, though it is possible that the value of the liability only dropped from $5.1 million to $4.9 million. Under Roll Call’s traditional accounting method, Pelosi’s overall liabilities dropped from $12.8 million to $8 million. Subtracting her minimum liabilities from her minimum assets, Pelosi’s minimum net worth appears to almost double, from $12.5 million in 2008 to $21.7 million in 2009.

House Minority Leader John Boehner (R-Ohio) reported assets valued at a minimum of $1.75 million in 2009, just above the $1.7 million that he previously reported.

Boehner, who lists no liabilities, did report a partial sale of his largest asset in December 2009, in a transaction valued at $1 million to $5 million.

That sale included Boehner’s “profit sharing retirement plan” from Nucite Sales Limited Partnership, the plastics and packaging firm that he headed before his election to the House.

Boehner reported no capital gains from the sale. He reported the subsequent purchase of a traditional IRA from UBS Financial Services, with dozens of stocks, bonds and government securities with a combined minimum net value of at least $873,000.

In the Senate, Majority Leader Harry Reid (D-Nev.) and Minority Leader Mitch McConnell (R-Ky.) each dropped all liabilities and reported slight gains over the previous calendar year.

Reid reported a minimum net worth of at least $3.06 million, up from the $2.88 million that he recorded in 2008.

He no longer lists a loan valued at $50,000 to $100,000 from Harry Reid Ltd., the “professional law corporation” of which he identifies himself as the president, trustee, sole owner and sole beneficiary. Reid had incurred the loan, which carried 10 percent interest, in 1983, according to his previous filing.

McConnell’s minimum net worth rises to at least $7.10 million in 2009, an increase from the $6.15 million he listed in calendar year 2008.

McConnell no longer lists any liabilities after he paid off the mortgage on his Capitol Hill townhouse in 2009, previously valued at $100,000 to $250,000.

He also dropped debts from his 2008 Senate campaign, valued at $1 million to $5 million in his previous report. McConnell reported closing those lines of credit in 2008.

Roll Call’s analysis of Members’ wealth is based solely on the information that lawmakers must provide in their annual 2010 financial disclosure reports, which cover calendar year 2009.

Roll Call determines each lawmaker’s minimum net worth by adding the lowest number in the range reported for each asset — for example, a $1 million to $5 million asset would be evaluated at $1 million — and subtracting the lowest total liabilities.

Although lawmakers are compelled to reveal information about assets, including investment accounts or rental properties, the disclosure process protects Members from divulging other economic indicators, such as the value of homes as well as antiques, vehicles and other valuables.