Australian pedestrian and cyclist deaths before and after helmet law.
Pedestrian deaths have been scaled to sit on top of the cyclist death line for comparison. There are more pedestrians killed than cyclists, so the cycling data looks more variable in comparison.
Can you see any effect of helmet law? If there is any effect it is very small. Deaths for both cyclists and pedestrians were going down in the late ’80s but progress has stagnated since then. What has caused the overall decline in deaths? Mostly it was due to massive ramping up of speed and red-light cameras, together with the introduction of demerit points. You can read the detailed history here. Real safety comes from preventing collisions and lowering speeds.
Update: a paper published in 2015 shows that the “odds ratio” test used to estimate the effectiveness of helmets is unreliable and typically overestimates the effectiveness of helmets. In the three studies for which sufficient data was available, an accurate measure of the risk ratio is possible and in all three cases the published studies had overestimated the effectiveness of helmets. See Overestimation of the effectiveness of the bicycle helmet by the use of odds ratios and PDF.
Thanks to Rebel Metropolis.org for the bar chart.