As charities around the country fret about deficit-minded politicians stripping away the tax benefits they enjoy, the Bill & Melinda Gates Foundation is paying for new research on how tax policies affect nonprofit groups.

The $1-million, three-year grant to the Urban Institute will help the Washington think tank study the impact of tax proposals such as reducing or eliminating the charitable deduction, revoking charities’ exemptions from property taxes, simplifying the excise tax, and requiring foundations to give away more of their money each year.

“We really believe that high-quality and timely data and research can raise the quality of policy debates and ultimately contribute to a policy environment that enables the charitable sector to thrive,” said Darin McKeever, Gates’s senior program officer for charitable sector support.

Mr. McKeever said that as a private foundation, the Gates fund does not take a position on any specific tax proposals.

Gates has been stepping up its giving over the past three years to organizations in its “charitable-sector support” portfolio, which includes nonprofits such as the Foundation Center and Independent Sector. It currently gives away roughly $7-million a year to such organizations.