Mortgage industry leaders have challenged the validity of the Australian Bureau of Statistics' first-home buyer data, saying it no longer gives a true picture of the number of people buying their first home.Participants in an industry roundtable hosted by Deloitte said changes to 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 the growing trend for parents to use retirement funds to buy properties for their children.According to the ABS, the proportion of first-home buyers in the market has fallen from around 20 per cent at the end of 2011 to around 12 per cent today.This change has prompted a lot of commentary about the apparent problem of affordability in major city markets, the need for more new housing and the question of whether foreign investors are crowding out other buyers.For the ABS, a first-home buyer is anyone who applies 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 buying an established house or unit may not be captured in the ABS data.Mortgage Choice chief executive, Michael Russell, said: "In the last 30 years there's been a fundamental shift in the expectations of first-home buyers, who now want to and expect to buy in either the area they were brought up, or in close proximity to their place of work."First-home buyers now are buying a far greater percentage of established property as opposed to new dwellings on the fringe."Additionally, we are not including in the first-home buyer count those genuine first-home buyers who are electing to buy an investment property in lieu of a property owned for occupation. This is a growing trend, yet their presence as first-home buyers is not accurately recorded.ANZ's general manager of mortgages and deposits, Brad Gravell, said: "In the last couple of years, the movement of activity from other segments is also clouding the data. The data on first-home buyers is not necessarily absolutely correct."The executive director of distribution at NAB Broker, Steve Kane, said: "At auctions it is actually mums and dads investing in units for their children for 10 or 15 years time."Russell said the first-home buyer numbers in Mortgage Choice's loan settlement data had remained fairly constant over the past few years.