From Roy Morgan Research:

Over the last four years the number of investment property loans in Australia has grown by 37% compared to an increase of only 4% in the number of owner occupied loans. These are the latest findings from the Roy Morgan Research Consumer Single Source survey of approximately 50,000 people per annum.

In 2010 just under a million (954,000) Australians 18+ had an investment property loan compared to an estimated 1.31 million as at March 2014. This growth represents an increase of 37%. Over the same period the number of Australians with an owner-occupied home loan increased from 4.66 million to 4.83 million, an increase of only 4%.

The growth in investment property loans over the last four years has come predominantly from the 35 to 64 age groups which account for 78% of the increase. The result is that 11.9% of the 50 to 64 age group now hold an investment property loan (compared to 9.4% in 2010) and 11.3% of the 35 to 49 age group had one (up from 8.5%).

Within the same time period the proportion of those aged 50 and over with an owner-occupied home loan has increased with the greatest growth being in the 50-64 age group, up from 31.6% to 34.0%. The under-35 age group on the other hand showed a decrease in the number and proportion with an owner-occupied home loan.