Rental price growth measures

Why is the Zoopla measure higher than the ONS?

How much are rental prices growing? The BBC headline was:

Rents rising at fastest pace in 13 years, says Zoopla

Zoopla’s UK Rental Market Report suggested private rents were growing by 4.3%. That annual changes compares the value in September 2021 to a year earlier. In contrast, the Office for National Statistics index shows annual growth at 1.3%.

Why are these figures so different?

Construction and deconstruction

The Office for National Statistics uses administrative sources. It collects data from government sources, including the Valuation Office Agency. These sources give about 520,000 annual private rents prices in the United Kingdom. The agencies send rental officers to collect prices paid for private rental properties.

The goal of its private housing rental price index is simple — to estimate changes in those prices. The sample of rents is not random, but officers seek to cover over one in ten rental properties. As the ONS documentation states:

The sample is not random but procedures are in place to ensure the collection is representative of the private rental market.

Analysts then gather a stratified random sample of properties from across the UK. That uses about half of all records in a 14-month period. Those strata are by nations and English regions…