본 연구는 인구구조 변화가 실질금리에 미치는 영향을 분석하기 위해 연령대를 가계의 금융행태를 기준으로 구분하는 방식과 연령그룹 계수를 다항식(Polynomial) 형태로 가정하는 방식을 사용하여 실증분석하였다. OECD 국가패널 자료를 사용하여 회귀분석을 수행한 결과, 차입수요가 많은 청장년층의 비중 증가는 실질금리를 상승시키는 방향으로, 순저축을 많이 축적하는 중고령층의 비중 증가는 실질금리를 하락시키는 방향으로, 그리고 순저축을 소진하는 시기인 최고령층의 비중 증가는 실질금리를 상승시키는 방향으로 영향을 주었다. 회귀분석 추정결과를 바탕으로 한국의 장래 인구구조 변화에 따른 실질금리 변동을 예측해 본 결과, 노동능력을 기준으로 연령을 구분하여 분석한 경우와 달리 2030년 부근에서 실질금리가 상승세로 전환하며 그 이후 상승속도가 빠른 것으로 나타났다.

Real interest rates are determined by the demand for and supply of funds in the financial market. Individuals influence the demand for and supply of funds through financial activities such as borrowing and saving. Financial behaviors, including borrowing and saving patterns, vary across different stages of life. This implies that different age groups have different impacts on real interest rates. Young adults, for instance, tend to borrow more for purposes like home purchasing and education, which acts as a factor driving interest rate increases. Middle-aged adults, including early elderly individuals, typically have the largest accumulated wealth and savings, leading to a decrease in real interest rates as their population increases. Subsequently, late elderly individuals tend to diminish their net savings through increased consumption or gifting, resulting in a decrease in net savings and a consequent rise in interest rates as their population grows. To measure the impact of population aging on real interest rates accurately, it’s essential to analyze how financial behaviors change throughout the life cycle. Existing empirical studies on the influence of demographic changes on real interest rates often categorize age groups based on labor force participation or use fixed age intervals (e.g., 20-year intervals) as explanatory variables. However, this approach fails to account for changes in financial behaviors across different age groups, potentially leading to inaccurate estimations of the impact of demographic changes on real interest rates. Particularly, it may overlook the effect of reduced net savings among the elderly population, resulting in an overestimation of the decline in real interest rates due to future population aging. In contrast to previous research that categorized age groups based on labor force participation, this study reclassified age groups based on changes in financial behaviors throughout the life cycle to analyze the impact of demographic changes on real interest rates empirically. Additionally, regression analysis was conducted assuming that the coefficients for age groups affecting real interest rates follow a polynomial form. The analysis revealed that an increase in the proportion of young adults leads to an increase in real interest rates, while an increase in the proportion of middle-aged adults leads to a decrease in real interest rates. Conversely, an increase in the proportion of late elderly adults leads to an increase in real interest rates. Using the estimated coefficients from this empirical analysis and population projections from the United Nations, the study derived how real interest rates would change in response to future demographic changes in various countries. Contrary to previous studies suggesting a continuous decline in real interest rates due to population aging, it was found that real interest rates are expected to rise between 2020 and 2030. Moreover, given the rapid pace of population aging expected in South Korea, the projected increase in real interest rates is notably high.