Proper use of denominators
The Herald, and the Ministry of Transport, are reporting rates for motor vehicle crashes and casualties, not just totals:
Statistically, Dunedin is New Zealand’s worst city for motor vehicle crashes and casualties but authorities say the numbers are dropping.
…
Last year the city recorded 364 injury crashes. Auckland had 2903, and Christchurch 715.
However, Dunedin had the highest number of crashes per 10,000 population (29), ahead of Palmerston North (24) and Napier (23).
Population is not the ideal way to standardise road crashes (especially in high-tourism areas), but it’s a lot better than not doing anything. When we looked at crashes at intersections, back in March, it didn’t make a lot of difference whether we standardised by population, number of registered vehicles, or vehicle-miles travelled.
Thomas Lumley (@tslumley) is Professor of Biostatistics at the University of Auckland. His research interests include semiparametric models, survey sampling, statistical computing, foundations of statistics, and whatever methodological problems his medical collaborators come up with. He also blogs at Biased and Inefficient See all posts by Thomas Lumley »