You're mixing up different statistics that aren't comparable. You also seem to be asking the wrong question, imho. The question isn't "How many cases of melanoma 'across the board' are caused by tanning beds?", but rather "Do tanning beds cause or contribute to the likelihood of getting melanoma?". Since there are very few 80 year old men using tanning beds or who have even ever used a tanning bed, the rate of melanoma among that group is irrelevant to the question being asked. It's still important in the study of the various causes of melanoma, but if we're looking at tanning beds in particular, then we need to look at the people who use them. That happens to be young women, and among young women, 76% of melanoma is related to the use of tanning beds. The fact that 24% of melanoma cases in that age and gender group are
not tanning bed related shows that people in that group sometimes get melanoma from other causes. The fact that over 3/4 of cases in that group
are tanning bed related shows that using tanning beds can greatly increase a person's chance of getting melanoma.
The TOG