The Australian Bureau of Statistics has started an investigation into the robustness of its estimates of how many loans are made to first-home buyers.A note accompanying the latest Australian Bureau of Statistics housing finance data said: "Concerns have been raised that under-reporting could occur if some lenders were only able to accurately report on those buyers receiving a first home buyer grant."The Australian Prudential Regulation Authority is contacting lenders on behalf of the ABS to investigate whether lenders experience any difficulties reporting on loans to first-home buyers. 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."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. 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.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.Previously the ABS has told Banking Day that "ABS data excludes persons entering the market for the first time to buy an investment property."In recent months, a number of commentators have challenged the validity of first-home buyer data. Research by Macquarie Securities and RFi, which was published in April, concluded that Australia's first-home buyers were morphing into first-home investors.Macquarie and RFi said much of the current investor demand for housing has been from young, middle to high income households and was actually "pseudo first-home buyer demand."The consensus among participants in an industry roundtable hosted by Deloitte in March was that changes to the states' first home owner grant schemes had distorted the data, as had the growing propensity of first-home buyers to enter the market as investors and for parents to use their retirement funds to buy properties for their children.The executive director of distribution at NAB Broker, Steve Kane, told the roundtable: "At auctions it is actually mums and dads investing in units for their children for 10 or 15 years' time."