Originally Posted by
mstateglfr
But we weren't talking specifically about people who end up in an ER.
I'm really not following.
Correct, you are not following.
Counting only injuries "severe" enough to result in an ER visit is a simple attempt to filter out the "falls" that result in no injury or minor injuries from consideration in order to more accurately evaluate the risk of the activity under discussion. But it is better than giving every "fall" an equal value in risk evaluation, regardless of the injury severity incurred as in "I say that across the US, there are more than 640 falls off a bike per day by people 15 or older."
People who do not understand how to evaluate risk will often quote data or factoids from so-called "studies" or even their own guesswork that is based on the use of vague undefined metrics like "falls" or "crashes" and give no consideration to the severity level of the injuries that typically occur from various types of "falls" and "crashes".
If you care to read more discussion that includes promotion for use of specific bicycling equipment or bicycling technique that rely on the use of faulty risk analysis "studies" that among other problems make no distinction between falls that result in boo-boo injuries that can be treated with a band-aid, and catastrophic injuries, try the Vehicular Cycling or Helmet sticky threads.