This is a visualisation of MBIE's Rental Bond data, collected from bonds lodged with the Tenancy Tribunal.

What are the colours? What are the dots?

The colours represent the change in the average (geometric mean) rent of new rentals compared with the same period the year before. Areas with very few new rentals are hidden because they tend to be too volatile.

The dots in the line chart show the number of new rentals in that period. Big dots mean a lot of new rentals started in that quarter.

What do the fluctuations mean?

There are strong seasonal patterns in many areas. For example, students tend to start their tenancy at the beginning of the academic year (Q1). This will lead to a high number of new bonds lodged (bigger dots), and sometimes a drop in the average rent. This doesn't necessarily mean that prices are falling for everyone. It could also mean that many cheap students flats are going on the market, which will bring the average down.

Similarly, in the last quarter there's often a student exodus, which might look like a price rise but actually be an absence of students starting new flats.

How does it compare with other data sources?

The MBIE data is more comprehensive than the TradeMe dataset because every bond has to be lodged with the Tenancy Tribunal. Breaking the data down into area units also gives us much better insight into what's happening in different parts of the city.

The MBIE data also uses geometric means to produce averages. This is a different way of calculating averages which gives equal weight to changes at the top and bottom ends of the housing market.