FRED now offers Optimal Blue Mortgage Market Indices, which provide a more-detailed look at mortgage rates. These indices are computed daily from actual mortgage closings and cover about 35% of the U.S. market.

The FRED graph above compares the weekly rates from Freddie Mac (red line) and from Optimal Blue (blue line). The latter also covers mortgages that aren’t managed by Freddie Mac, but with the restriction that they must be “conformable”—that is, the loan amount can’t exceed the limit for the property and its location.

In the second graph, we see that the loan amount influences the loan rate: The closer your loan is to the full value of the house, the more you have to pay. But the difference doesn’t look too large or unpredictable. Keep in mind, though, the composition of the loans for these two series may change for reasons that may correlate with the size of the loan: for example, the creditworthiness of the borrower.

So our last graph looks at different levels of creditworthiness—specifically, the FICO score of the borrower. The differences between the series don’t look dramatic, but borrowers definitely care about them. The difference between the rate for the highest score and the rate for the lowest score is about half a percentage point, which actually can add up significantly over 30 years.

How these graphs were created: For all graphs, start from the relevant release calendar. For the first, select the conforming series, and click “Add to Graph.” From the “Edit Graph” panel, use the “Add Line” tab to search for and select the average 30-year mortgage. For the second and third graphs, select the relevant series in the release table and click “Add to Graph.”

Suggested by Christian Zimmermann.