These are two of the pages sumitted to the Australian NRSS during 2011. Completely ignored by the authorities. The first page uses Australian Bureau of Statistics data from 1985/86 re cyclist numbers per day across Australia, different states and cities, and compares it with various surveys since the law was introduced. Note that cycling popularity was reportedly increasing by about 10% per annum in the 1980s, so cyclist numbers were probably quite a bit higher than the 85/86 ABS data by the time the helmet law was first introduced in 1990. 

The second page considers all road user accidents/injuries, including car vs car, when tens or hundreds of thousands of discouraged cyclists instead drove their vehicles. This analysis seems to go down like a lead balloon with other helmet law researchers. The stats show a steady decline in Australian road casualties before the introduction of helmet laws in 1990/92, after which casualties increased significantly. The assertion might be controversial, but it's a powerful and logical argument with supporting evidence - less cyclists = more car drivers = greater traffic density = more accidents = more chance everybody is at increased risk of injury, whether or not they ride a bike.

This page was written by Chris Gillham in defence of a published study by Chris Rissel, The impact of compulsory cycle helmet legislation on cyclist head injuries in New South Wales, Australia. The page has lots of evidence and supporting graphs.

New Zealand is the only country apart from Australia which actively enforces mandatory all-age bicycle helmet laws nationally (although adults are exempt in the Northern Territory of Australia). The law was enforced in New Zealand in January 1994.