How to compare two HDB towns without fooling yourself

Two town medians side by side look like an answer. Most of the time they are a question in disguise, because the two numbers are rarely computed over the same kind of thing.

1. The window

Each area here uses the shortest window in the 12, 18, 24-month ladder that gives it at least 30 resales. A busy town gets 12 months; a quiet one may need 24, and an area that cannot reach 30 resales even at 24 months publishes its count instead of reaching further back: Singapore prices moved 28 per cent over five years, so a longer window would blend a cheaper market into today’s figure. A 12-month median and a 24-month median are still different statistics, and the comparison pages say so when the two towns differ. Check the window before you trust a gap.

2. Flat type

A town whose resales are mostly three-rooms will show a higher PSF than a town of five-rooms even if a like-for-like flat costs the same in both. Use the by-flat-type table on each town page rather than the headline when you are comparing.

3. Lease

A mature town with a median lease of 60 years and a new town at 90 are not comparable at the headline. The lease band charts let you compare band against band, which is the only version of the comparison that means anything.

4. Floor

Less important than the other three, but the same principle: if one town’s stock is taller, its median carries more high-floor transactions.

Then compare

The comparison pages put two towns side by side on price, lease and volume with the windows stated. Start there, then open both town pages and compare the same flat type and the same lease band. It is four lookups instead of one, and it is the difference between a comparison and a coincidence.