Recent tax legislation has increased the availability of low-income housing tax credits nationwide by as much as 50%, but the pool of investors has not grown as much, driving down the price per credit and pushing yields higher for the shrinking group of banks and insurance companies that dominate the sector. The Richman Group reports that the investor base looks nothing like it did decades ago, when major corporations regularly invested. The mismatch is leaving some deals unable to raise sufficient financing, raising questions about how many of the projected affordable units will actually come to fruition.