Heightened prudential supervision of lending in the residential housing market has begun to generate sustained monthly falls in the value of loans made to investment borrowers.Monthly housing finance data published by the Australian Bureau of Statistics shows that growth of lending to investors in trend terms declined by 1.5 per cent to A$12.4 billion in May 2017 compared to the previous month.That equated to a $194 million slide in investment home loan activity compared to April.It was the fourth consecutive month that the trend in investment lending fell and the rate of decline is accelerating. Sean Keane from Triple T Consulting, in a commentary for Credit Suisse, aired a common view -  that the dampening investment activity relates almost entirely to the macroprudential measures imposed on lenders by the Australian Prudential Regulation Authority in late March."APRA's macro-prudential measures and the very noticeable behavioural changes in lending practices by the major banks, are having a clear impact on local activity - especially in the investment segment," Keane stated in a note to clients."Investment lending now makes up just over 37 per cent of the total dwelling commitments undertaken in May, a number which is well down on the 45 per cent market share seen in the middle of 2015."Westpac senior economist Matthew Hassan said he expected growth in investment lending to taper further as the impact of sharp investment loan repricing in June and July by the major banks washes through the property market."The cumulative change in interest rates is now substantive with an average rate change of 28 basis points similar to that seen during the last round of macro-prudential measures in 2015," he said."Markets are clearly responding with auction clearance rates in Sydney and Melbourne off from the highs at the start of the year." The latest official trend data in the investment segment of the housing credit market appear to confirm forecasts made in March by research firm CoreLogic that lending to investment borrowers was unlikely to regain momentum in the medium term.CoreLogic cited the prospect of rate rises and record low rental yields as the likely drivers of tapering demand for investment mortgages.While growth in May housing-related credit was weighed down by the regulatory clampdown on investment lending, the value of loans made to owner-occupiers continue to rise according to the ABS' trend and seasonally adjusted measures.Lending commitments made to owner-occupiers increased by 0.4 per cent in May to $20.42 billion in trend terms.More first homebuyers entered loan contracts in May, with this segment of the market accounting for 14 per cent of all new loan commitments - up from 13.8 per cent in April.The ABS estimates that the average loan size for first homebuyers rose by $900 in May to $318,000.However, there was a more dramatic increase in the average size of total owner-occupier commitments, which soared $8100 to 380,000."The strong growth in lending to owner-occupiers in today's data, and the return of the first home buyer, certainly provide some support to the housing market, and they