Mortgage Supply, LTV and Risk Pricing

Abstract

This paper focuses on mortgage supply and its contribution to the loan-to-value (LTV)-ratio. The paper starts by finding the optimal LTV-ratio for a profit-maximising mortgagee that supply mortgages using housing as collateral. As the LTV-ratio represents the mortgagee's risk exposure, the optimal LTV-ratio is one where the mortgagee is paid for its actual risk exposure. Thinking in terms of social welfare, the profit-maximising LTV-ratio is also optimal for society in our supply side framework. When including additional characteristics from the supply side of the mortgage market, the paper shows how the profit-maximising LTV-ratio varies according to moral hazard, risk pricing, funding structures, lending volumes and collateral values. The supply side characteristics create a wedge between the profit-maximising LTV-ratio and the LTV-ratio optimal for society. The model helps understand the role of mortgage supply in the period preceding the financial crisis, where LTV-ratios increased considerably. Consequently, it also allows for straightforward arguments regarding macro-prudential policy. Highlighting risk exposure, the paper continues by analysing the risk pricing response to falling house prices and an LTV-ratio that exceeds the LTV-ratio at origination. The paper finds a kinked-relation between the mortgage rate and the LTV-ratio ex post, separating risk pricing ex ante and ex post.