Sure, but it provides some grounds to get money for a study on it. Pedestrian deaths are basically free from the CDC, and population is free from the Census.

Sure, but it provides some grounds to get money for a study on it. Pedestrian deaths are basically free from the CDC, and population is free from the Census. More detailed data would require studies, unless someone is publishing a nation-wide count of pedestrians that I'm not aware of. There's always better data, and making a study that doesn't have any spurious correlations is extremely expensive. Pedestrian growth is also not necessarily linearly correlated to pedestrian fatalities. If cities become more walkable, it could be that there are more pedestrians walking shorter distances. I would expect that to impact fatalities per pedestrian less than having more pedestrians walking the same amount. This data just says that the growth in population isn't likely the direct cause of the effect. It could be a difference in the demographics of the population (new people walk more/less). It could be a difference in the existing pedestrians (i.e. % of pedestrians is constant, but people are walking at night or with headphones, etc). It could be a difference in the existing drivers (more dangerous cars, more dangerous driving, more DUIs, etc).