The Urban Institute’s Housing Finance Policy Center issued its May 2016 Housing Finance at a Glance Chartbook. This monthly report is invaluable for those of us who follow the mortgage market closely. The mortgage market changes so quickly and so much that what one thinks is the case is often no longer the case a few months later. This month’s report has new features, including Housing Credit Availability Index and first-time homebuyer share charts. Here are some of the key findings of the May report:

• The Federal Reserve’s Flow of Funds report has consistently indicated an increasing total value of the housing market driven by growing household equity in each quarter of the past 2 years, and the trend continued according to the latest data, covering Q4 2015. Total debt and mortgages increased slightly to $9.99 trillion, while household equity increased to $13.19 trillion, bringing the total value of the housing market to $23.18 trillion. Agency MBS make up 58.2 percent of the total mortgage market, private-label securities make up 6.1 percent, and unsecuritized first liens at the GSEs, commercial banks, savings institutions, and credit unions make up 29.4 percent. Second liens comprise the remaining 6.4 percent of the total. (6)

It is worth wrapping your head around the size of this market. Total American wealth is about $88 trillion, so household equity of $13 trillion is about 15 percent of the total. With debt and mortgages at $10 trillion, the aggregate debt-to-equity ratio is nearly 45%.

• As of March 2016, debt in the private-label securitization market totaled $613 billion and was split among prime (19.5 percent), Alt-A (42.2 percent), and subprime (38.3 percent) loans. (7)

This private-label securitization total is a pale shadow of the height of the market in 2007, back to the levels seen in 1999-2000. It is unclear when and how this market will recover — and the extent to which it should recover, given its past excesses

• First lien originations in 2015 totaled approximately $1,735 billion. The share of portfolio originations was 30 percent, while the GSE share dropped to 46 percent from 47 in 2014, reflecting a small loss of market share to FHA due to the FHA premium cut. FHA/VA originations account for another 23 percent, and the private label originations account for 0.7 percent. (8)

The federal government, through Fannie Mae, Freddie Mac and Ginnie Mae, is insuring 69 percent of originations. Hard for me to think this is good for the mortgage market in the long term. There is no reason that the private sector could not take on a bigger share of the market in a responsible way.

• Adjustable-rate mortgages (ARMs) accounted for as much as 27 percent of all new originations during the peak of the recent housing bubble in 2004 (top chart). They fell to a historic low of 1 percent in 2009, and then slowly grew to a high of 7.2 percent in May 2014. (9)

It is pretty extraordinary to see the extent to which ARMs change in popularity over time, although it makes a lot of sense. When interest rates are high and prices are high, more people prefer ARMs and when they are low they prefer FRMs.

• Access to credit has become extremely tight, especially for borrowers with low FICO scores. The mean and median FICO scores on new originations have both drifted up about 40 and 42 points over the last decade. The 10th percentile of FICO scores, which represents the lower bound of creditworthiness needed to qualify for a mortgage, stood at 666 as of February 2016. Prior to the housing crisis, this threshold held steady in the low 600s. LTV levels at origination remain relatively high, averaging 85, which reflects the large number of FHA purchase originations. (14)

It is hard to pinpoint the right level of credit availability, particularly with reports of 1% down payment mortgage programs making the news recently. But it does seem like credit can be loosened some more without veering into bubble territory.

Hard to keep up with all of the changes in the mortgage market, but this chartbook sure does help.