Owner occupier commitments by lenders can be expected to record modest increases in August, perhaps slightly higher than the 0.3 per cent rise in July, the RP Data Mortgage Index shows.The RP Data Mortgage Index measures valuation-related mortgage activity, in effect in real time, providing insights six weeks ahead of the official ABS data.The release of the Australian Bureau of Statistics (ABS) housing finance data on October 10, covering activity for the month of August, will be viewed more closely than ever before following recent comments by the Reserve Bank in its bi-annual Financial Stability Review.The RBA said in the FSR last week that: "the composition of housing and mortgage markets is becoming unbalanced, with new lending to investors being out of proportion to rental housing's share of the housing stock."RP Data facilitates the transmission of around 95 per cent of all full valuation reports for residential mortgage lending purposes across the country. RP Data compiles this Mortgage Index on the basis of demand for these valuations, as a proxy for demand for loans.The correlation of the RP Data Mortgage Index with the ABS housing finance data is 86 per cent.  As can be seen from the first chart ("RMI matches ABS", above), there is a very high correlation between the number of requests for valuations on RP Data's platform and the number of owner occupied lending commitments, as reported by the ABS.  The second graph ("RMI's monthly prediction", below) shows the even higher correlation between the monthly change in the number of requests for valuations and owner occupied loans. It is important to remember that owner occupier commitments still make up approximately 60 per cent of total housing finance, even though investor loan activity has recently been driving growth in the market.Based on RP Data's RMI, NSW has seen the strongest level in activity in August, with only Tasmania recording a fall.But what about the level of investment lending activity?  Unfortunately this is tougher to get a handle on, given the ABS doesn't report on the number of dwelling commitments for investment lending, only the overall value.  As a general observation, RP Data has recently been seeing a consistent increase in mortgage related activity events across its platforms, albeit still below the recent highs set in early 2014 and late 2013.  However with spring a seasonally strong time for the market, RP Data expects mortgage related activity to maintain its upwards trajectory, barring any regulatory intervention or other external shocks.