Prayk's market observation system collects prices of listings published in the last 90 days and processes them statistically every night: medians and quartiles are computed, outliers are excluded.
Figures are asking prices from listings, not actual transaction prices. Outliers are excluded from the statistics; only groups with at least 8 listings are shown. "Time to sell" is the median lifetime of a listing before it leaves the market. Yield is a gross figure: taxes, repairs, utilities and vacancy are not taken into account.