I found the figure ages ago worked but can't find it now (haven't looked too hard to be honest) so a bit of a homework assignment I'm afraid
DISCLAIMER: The maths below might be bad .. I think it's OK though -- someone, say why I'm wrong!
Here:
http://en.wikipedia.org/wiki/File:Cause ... p_(percent).png
Wow, more than one in every five 15-24 year olds that die are by being shot dead. wow.
Anyway, back to the task in hand, Open excel
Right .. we're going to work out the average of the light blue line, as this is our answer. Here's the important kick: Each 'point' in the light blue line <> an identical number of years -- best do a row per age per year (so, for example, the second column 1-4 years should involve you typing in that figure 4 times, the third column, 10 times) as we're going to get the average.
Type in the percentages in (so to repeat the first 'light blue dot' will deserve just 1 number, the second (aged 1-4) will deserve 4 numbers, etc - hope this makes sense. For 85 years + let's do 10 years, sounds about right.
Find the average of all the numbers you've entered (divide by the number you've entered). And that's your mathematical answer. Unless I've got something mathematically wrong, which isn't impossible
Soooooo .. about 1.2% of Americans will end up shot dead sooner or later!