You are talking about your bank's "penetration rate" lending in the LMI geographies. That is compared by examiners to a number of variables, one of which is the market-driven penetration rate of all lenders in your uniquely defined Assessment Area. So if 10% of your HMDA-reportable mortgages are in your AA LMI tracts one comparison would be to the compiled experience of all other lenders. Let's say you have 100 AA mortgage loans of which 10 are in your LMI tracts. That would be a 10% penetration rate. If there are 10,000 mortgages reported by all lenders in your AA and 1500 are in the AA LMI tracts, then the market penetration would be 15%. That is one number to which you will be compared. The calculation is done both for units and dollars originated. Obviously, if you are 10% and the market is 15% then the question is why are you only 2/3 the market experience. That is when you need to know the story behind the numbers. It also is good market analysis to understand your markets and the competition.
You can get the market data from the FFIEC database which is free or you can order from a commercial source such as GeoDataVision which is inexpensive (but not free) and has all the market data calculated and organized to show not only penetration rates but market rank and market share too.
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