Is there an 'invisible boundary line' between 20% and 30% repayment ratio?

When considering the amount of housing loan borrowing, the idea that 'the repayment ratio should be around 20-30%' has been used as one indicator. However, what does this standard mean in reality for households? In this report, based on survey results, we will verify whether there are differences in ① the presence or absence of regret, ② the burden of repayment, and ③ the balance between repayment and asset formation, between a repayment ratio of 20% and 30%.

【Summary】

・Approximately 35% of those repaying housing loans have some regret about the housing loan

・The most common regret is 'the borrowing amount was too much'

・As the repayment ratio increases, the number of people who regret it also increases. In particular, there is a significant increase from a repayment ratio of 20% (38.5%) to 30% (46.4%)

・There is a 'boundary line' between a repayment ratio of 20% and 30% where the burden increases

・At 20%, the 'balance group' that balances repayment and asset formation is dominant, but at 30%, the 'repayment priority group' that prioritizes repayment is dominant, reversing the relationship

From the perspectives of 'increased regret,' 'amplified burden,' and 'difficulty in balancing asset formation,' reaching 30% may exceed the household's tipping point

The impact of repayment ratio on the presence or absence of regret

First, when asked about the 'presence or absence of regret about the housing loan,' 35.2% of households repaying housing loans answered 'regret present' (Table 1). The most common reason for regret was 'I should have borrowed less (28.3%),' followed by 'I should have had a higher down payment (27.2%)' (Table 2). Both of these are due to 'the borrowing amount being too much,' and compared to regret about interest rates or repayment periods, this is strongly evident.

【Table 1】Presence or absence of regret about housing loans

※Respondents: 6,062 people currently repaying housing loans (Source: Unless otherwise specified, based on the 'Survey on Awareness and Reality of Housing and Asset Formation' (2026) by the Mirai Research Institute of Sumitomo Mitsui Trust Asset Management)

【Table 2】Reasons for regret about housing loans (multiple answers possible)

※Respondents: Among those currently repaying housing loans, those who answered that they have regret about the housing loan

This 'regret about the borrowing amount being too much' intensifies in stages as the repayment ratio increases (Table 3, brown bar graph). Furthermore, looking at the overall level of regret about housing loans, while it remains at 38.5% for a repayment ratio of 20%, it significantly increases to 46.4% for a repayment ratio of 30% (Table 3, orange bar graph). The increase in the repayment ratio not only heightens the regret of 'borrowing too much' but may also push up overall regret, including other regrets.

【Table 3】Presence or absence of regret about housing loans by repayment ratio

※Respondents: Those currently repaying housing loans (excluding those who answered 'unknown' for repayment ratio) * Among those who chose either or both 'I should have borrowed less' and 'I should have had a higher down payment' for the items they regretted

The 'invisible boundary line' reflected in burden and behavior

Changes can also be seen in the burden of loan repayment between a repayment ratio of 20% and 30%.

The percentage of those who answered that they 'feel a considerable burden' for repayment is 6.8% for a repayment ratio of 20%, but doubles to 13.9% for a repayment ratio of 30% (Table 4). Additionally, 'feeling burdened' also increases from 22.4% to 28.9%, suggesting that there is a 'boundary line' between a repayment ratio of 20% and 30% where the burden increases.

【Table 4】Burden of housing loan repayment by repayment ratio

※Respondents: Those currently repaying housing loans (excluding those who answered 'unknown' for repayment ratio) ※Less than 5.0% is omitted in the graph

Furthermore, a similar boundary line can be seen in household behavior towards asset formation. Looking at the way of thinking about balancing housing loan repayment and asset formation, while the 'balance group' that 'takes on both housing loan repayment and asset formation simultaneously' is 40.8% for a repayment ratio of 20%, it decreases to 28.1% for a repayment ratio of 30% (Table 5). On the other hand, the 'repayment priority group' that is 'prioritizing repayment, making asset formation difficult' increases from 32.8% to 42.6%, an increase of approximately 10 points.

In other words, while the balance group is dominant for a repayment ratio of 20%, for a repayment ratio of 30%, repayment priority prevails, reversing the relationship between the two.

【Table 5】Way of thinking about balancing housing loan repayment and asset formation by repayment ratio

※Respondents: Those currently repaying housing loans (excluding those who answered 'unknown' for repayment ratio)

From the above, although the repayment ratio has been generally considered to be 'within 20-30%,' in reality, there is a significant difference between 20% and 30%, and from the perspectives of 'increased regret,' 'amplified burden,' and 'difficulty in balancing asset formation,' it is suggested that reaching 30% may exceed the household's tipping point.

Since housing loans are long-term debts, it is necessary to consider the risk of increased repayment burden in the future due to changes in the environment such as reduced income or increased interest rates. Therefore, it is important to consider not only the current household situation but also the future, and to set the borrowing amount at a level with some margin at the time of borrowing.

However, there is also a choice to 'extend the borrowing period to lower the repayment ratio,' but caution is needed. While the monthly burden may be lighter, the interest amount to be paid will increase. Adjusting the borrowing period to lower the repayment ratio does not necessarily lead to improved household finances and may not be a fundamental solution. Considering these points, financial institutions and experts should not only present the repayment amount but also explain the impact of that level on future choices and household behavior. Additionally, borrowers themselves should consider not only the immediate repayment burden but also the long-term impact on their household finances and make careful judgments. These factors are considered to lead to less regret in home acquisition and stable household management thereafter.

◆In addition to this report, reports on various themes are posted on the Mirai Research Institute's website (https://mirai.smtb.jp/category/report/). Please take a look.

◆Inquiries regarding article content and survey results

Sumitomo Mitsui Trust Bank Sumitomo Mitsui Trust Asset Management Mirai Research Institute (Yano)

E-MAIL: mirai@smtb.jp

【Survey Overview】

(1) Survey name: 'Survey on Awareness and Reality of Housing and Asset Formation' (2026)

(2) Survey target: Nationwide 18-69 years old, excluding those working in related industries (finance, research, media, advertising)

(3) Survey method: Web survey

(4) Survey period: January 2026

(5) Sample size: 6,062

(6) Notes

Due to rounding, the percentages in the tables based on survey results may not add up to 100%

This report only analyzes those with experience using housing loans, so weighting back is not performed. There may be differences in numbers due to the presence or absence of weight correction with past housing loan-related reports and other reports.