The Australian Bureau of Statistics and the Australian Prudential Regulation Authority are reviewing the way lenders and brokers gather information about first-home buyers, to determine whether there is under-reporting of first-home buyer participation in the mortgage market.Following a report in Banking Day on Tuesday, which said that mortgage industry leaders had challenged the validity of ABS first-home buyer data, the ABS responded in an email: "The ABS acknowledges that some lenders' information systems may not have the capability to report first home-buyers according to instructions, particularly for buyers who are not claiming the grant."The "grant" refers to the first home owner grant. Some lenders are understood to have configured their management information systems in a way that identifies a first-home buyer by asking borrowers if they have applied for a first-home owner grant.However, several states have changed the conditions of their grants, so that only people buying newly-built properties are eligible. A first-home buyer purchasing an established house or unit may not be captured in the data.Banking Day made an error when it reported: "For the ABS, a first-home buyer is anyone who applies for a first home owner grant."In fact, for the purposes of its monthly publication, 'Housing Finance Australia', the ABS gets most of its data from APRA. APRA, in turn, has an instruction guide for reporting housing finance, which it issues to authorised deposit-taking institutions. On the question of first home buyers, the guide says: "A first-home buyer is a borrower entering the home ownership market for the first time."Where the ABS collects its own housing finance data, it issues the same instruction to lenders.Precisely how lenders determine who is a first-home buyer is not spelled out. That question will be looked at in the review and there will be a particular focus on the role grant applications play in that process.Distortions created by changes to grant schemes are not the only issue. Lenders and brokers say the growing propensity of first-home buyers to enter the market as investors and the trend for parents to use their retirement funds to buy properties for their children also muddy the water.The ABS said: "ABS data excludes persons entering the market for the first time to buy an investment property."