1) The distance-decay model
A simple way to think about walk-time is a decay curve. Investors often treat “within the same ward” as comparable, but Tokyo’s station micro-economies make that a weak proxy.
Price per m² = P₀ × e^(−β × WalkMinutes)
β is usually station-specific and line-sensitive. It can steepen beyond ~8–10 minutes for smaller layouts, and flatten for layouts with stronger amenity support.
2) A workflow you can use today
- Collect station-tagged sold comps (size, vintage, walk minutes).
- Clean obvious errors and winsorize tails by station + vintage.
- Fit β and control for age and layout.
- Compare live listings to the fair-value curve; price risk accordingly.
3) What to watch
- Breakpoints around 5, 8 and 12 minutes — sometimes tied to interchange convenience and route options.
- Age × distance interaction (older stock can be more sensitive beyond ~10 minutes).
- Layout effects: liquidity vs yield trade-offs behave differently by walk-time bucket.
Continue reading: Impact of Distance-to-Station on GRM & Yield