Ease of access to jumbo mortgage loans drove the Mortgage Bankers Association's (MBA's) Mortgage Credit Availability Index higher in September. The Index rose 0.9 percent to 183.4. An increase in the Index indicates that lending standards are easing.

The index has four components; the Government MCAI which decreased 0.6 percent and the Conventional MCAI which rose 2.4 percent. There are two indices housed within the Conventional MCAI, the Conforming Index which fell 1.1 percent and the Jumbo which jumped by 4.7 percent, hitting a record high.

This is a sharp reversal of last month's index report. The August MCAI suffered the largest decline in its history, falling 3.9 percent. Each of the four components dropped by more than 3 percent.

"Credit availability increased slightly in September, driven by a 5 percent increase in the supply of jumbo loans. The jumbo index, which grew from a combination of lower credit score requirements, non-QM loans, and investor products, is now at a record high since tracking began in 2011," said Joel Kan, Associate Vice President of Economic and Industry Forecasting. "Meanwhile, the trend of tightening credit availability in conforming and government programs continued over the past few months, as both indices decreased."

The MCAI is calculated using several factors related to borrower eligibility (credit score, loan type, loan-to-value ratio, etc.) gathered from over 95 lenders and investors. These are combined with data from Ellie Mae's AllRegs proprietary product to calculate a summary measure indicating the availability of mortgage credit at a point in time

The MCAI and its components were benchmarked in March 2012 and are designed to show relative credit risk/availability for their respective indices. The main index, Conforming, and Jumbo sub-indices were indexed at 100 while the Conventional and Government indices were indexed at 73.5 and 183.5 respectively to better represent where each index might have been relative to 100.