Students of the mortgage market will have access a new weekly measure of demand in the next month or so, courtesy of research firm RP Data.The firm plans to publish a "mortgage activity index" that will aggregate data largely drawn from applications for loans where the lender's credit-scoring engines check valuations with RP Data. Tim Lawless, head of research, said the index will be "based on analysis of metadata across our various valuation platforms."Because our valuations cover a large proportion of mortgage volumes this gives us a good indicator of finance commitments in the ABS [Australian Bureau of Statistics] data."Lawless said the activity index has an 86 per cent correlation with ABS data and will be available a month a half earlier.Australian Finance Group, which aggregates loan demand from brokers, presently produces a monthly sales index based on its own sales volumes.