ผลของการเปลี่ยนแปลงอัตราดอกเบี้ยเงินกู้เพื่อที่อยู่อาศัยที่มีต่อเงินงวดผ่อนชำระและระยะเวลาการกู้ยืม

Abstract

Adjustable Term Mortgage was first used in Thailand between 1984-1985 by the Government Housing Bank as it began to issue housing loans with floating rates and developed techniques to reduce the effects of interest rate fluctuations. This was accomplished by allowing loan maturity to be adjusted automatically to keep the installment payment constant. Furthermore, a margin was added to the installments computation to increase the ability to absorb future interest rate increases. Over time, the techniques have been widely adopted by other financial institutions in Thailand. Recently, financial institutions have begun to increase mortgage rates again. The purpose of this research is to study methods of housing installment calculation in the adjustable term mortgage system, and to analyze the results of change in interest rate on monthly installment payments and terms of mortgages. The sample group consists of the top seven Thai banks which, in total, control a 90 percent share of the housing loan market The research is divided into two parts. The first part consists of interviews of mortgage loan officers in seven banks together with secondary data on housing loan calculation methods and the specification of mortgage rates (as of 19 January 2006). The second part consists of formulating a housing loan calculation model from the data gathered in the first part, in order to analyze the impact of change in mortgage rates on monthly installment payments and terms of mortgages. The results can be summarized as follows: 1. All 7 banks use similar methods to calculate monthly installments, with the loan amount, terms of mortgage, and mortgage rate as the main determinants. However, each bank uses a different level of margin, between 0%-2%, and also differs in the patterns of payments, which is either step-up payments or constant payments. 2. When the mortgage rate changes, the terms of mortgages will be adjusted automatically. This means that when mortgage rates rise, the installment still does not change as long as the interest portion does not exceed the installment. On the other hand, if the mortgage rates fall, the principal part of the installment will decrease faster (as the borrower pays the same amount of installment), so the terms of the mortgage is shorten and borrower can repay the loan before the original ending period in the loan contract. 3. The ability to absorb effects of interest rate fluctuations is different for each bank. As the mortgage rate changes from teaser/discounted rate to floating rate, the installment of each bank can absorb about 2.50-4.00% rise in MRR/MLR (using the rates at the time of study). It depends on the margin which each bank added. The banks that add a higher margin can absorb more interest rate fluctuation than the banks which add a lower margin or no margin. However, a higher margin may result in the reduction of the effective loan limit. Some banks increase thein come ratio limit for borrowers, so the effective loan limit will not decline too much. In conclusion, under the adjustable term mortgage system, nearly all banks calculate installments such that they can absorb high interest rate fluctuation early on, by adding a margin to the calculation. As a result, when mortgage rates change, banks do not need to increase installments. Instead, they let the terms of mortgages be adjusted automatically as long as the interest rate payment does not exceed the installment. This reduces default risk by borrowers from interest rate fluctuation and effectively helps both the banks and the borrowers manage risk during periods of rising interest rates