Residential property investors may be presenting themselves as owner-occupiers when they apply for mortgage finance in a bid to beat the investor rate premiums that lenders have imposed.UBS banking analyst Jonathan Mott sent out a note to clients last week, speculating that investors were engaging in a bit of "reclassification".Mott said this would explain the dramatic slowing in investor mortgage balances and the offsetting acceleration of owner-occupier balances in the second half of last year.He said that if his speculation proved correct it might prompt the regulators to consider additional macro-prudential measures to take risk out of the mortgage market. According to the Reserve Bank lending data released last Friday, lenders' investor mortgage balances grew by 0.3 per cent in December, compared with the previous month.Over the 12 months to December lenders' investor mortgage balances grew by 8.5 per cent. The annual growth rate peaked at 11 per cent in May and June.Owner-occupier balances grew by 0.7 per cent in December, compared with the previous month, and by 6.8 per cent over the 12 months to December.Month-on-month growth in investor mortgage balances peaked at 0.9 per cent between March and June then started to slow. Owner-occupier balances started picking up in August.Mott said he was sceptical about the quality of credit data around the issue."The apparent slowdown in investment property lending and the almost exactly offsetting pick-up in owner-occupied appears indicative of changing behaviour by customers and brokers around designating the purpose of the mortgage," he said.