http://well.blogs.nytimes.com/2013/10/21/how-safe-is-cycling-its-hard-to-say/?hp

Who is right? Although many cyclists have strong opinions on the
safety of their sport, the answer is that no one really knows how safe it is, or
whether its safety has changed over the years.

It’s not that there is a lack of data. Instead, it is that the data are
inadequate to answer the questions.No one has good statistics, for example, on
crashes per mile ridden. Nor do the data distinguish road cycling on a fast,
light, bike with thin tires from mountain biking down dirt paths filled with
obstacles or recreational cycling on what the industry calls a comfort bike. Yet
they are very different sports.