The Housing Finance Policy Center’s latest credit availability index (HCAI) shows that mortgage credit availability declined to 5.1 in the second quarter of 2017, after reaching a recent peak of 5.4 in Q1 2017.

This decline was mostly driven by a shift in market composition, with the government channel losing market share to the portfolio channel, where lending standards are tighter, according to the Urban Institue, publisher of the report. In the meantime, credit continued to expand within the GSE and government channels, thanks to higher interest rates and lower refinance volumes.

The HCAI measures the share of home purchase loans that are likely to default—that is, go unpaid for more than 90 days past their due date. A lower HCAI indicates that lenders are unwilling to tolerate defaults and are imposing tighter lending standards, making it harder to get a loan. A higher HCAI indicates that lenders are willing to tolerate defaults and are taking more risks, making it easier to get a loan.

Mortgage credit availability in the government-sponsored enterprise (GSE) rebounded to 2.4 since its low of 1.4 in 2011. Both the government (FVR) channel and portfolio and private-label securities (PP) channel remain close to or at record lows. The FVR channel includes the Federal Housing Administration, the US Department of Veterans Affairs, and the US Department of Agriculture Rural Development programs.

Significant space remains to safely expand the credit box, according to the Urban Institute. If the current default risk was doubled across all channels, risk would still be within the pre-crisis (2001–03) standard of 12.5 percent for the whole mortgage market.