The recent strong growth in housing finance for investors, relative to owner-occupiers, is not a new phenomenon. Growth in the number of investment property loans has outpaced growth in owner-occupier loans for the past four years.According to Roy Morgan Research, 954,000 Australians had an investment property loan in 2010. The number has grown to an estimated 1.3 million at March this year - an increase of 37 per cent over four years.The number of Australians with an owner-occupier mortgage grew from 4.66 million to 4.83 million over the same period - an increase of only 3.6 per cent.The proportion of Australians in the 35 to 49 age group with an investment property loan has increased from 8.5 per cent to 11.3 per cent over the four years, while the proportion in the 50 to 64 age group has increased from 9.4 per cent to 11.9 per cent.Interestingly, the proportion of Australian under age 35 with an owner-occupier home fell over the four years.This observation lends credence to recent speculation that a growing number of young people are opting to enter the residential property market by buying an investment property rather than a first home.