The best information I could find goes back to 1999 from this CDC web site.
You can see that for white people (top green line) the rates has been increasing slowly and steadily for about ten years. I could not find evidence on the site for what was reported earlier than this.
Interestingly skin cancer seems to be a phenomena significant only to white people - other races are impacted but a very low rates (other statistics here from the American Melanoma foundation).
Now if the sun were the problem I would imagine that skin cancer would be commonly reported the further south that you go. So, for this CDC site, I grabbed this image:
This is rather counter-intuitive at first glance. Most of the heavier rates (darker colors, rate per 100,000 people) are in the pacific northwest, north and far northeast of the US. There are some higher rates on the US east coast as well. But in the states where I would think it would be highest, e.g., Florida, Texas, Louisiana, Arizona, New Mexico - the incidence rate is the lowest.
Now Arizona gets far more sun than Minnesota does - yet there is more skin cancer the farther north you go (at least in some directions).
So what about death rates from skin cancer?
I took this image from the same CDC site (I modified the colors so that the redder the state the higher the skin cancer death rate):
Here one sees some unexpected results: not all the states with the highest incidence rates have the highest death rates - South Dakota, with one of the lowest incidence rates has one of the highest death rates and Minnesota, with one of the highest incidence rates has one of the lowest death rates.
Further, one imagines that in Texas and New Mexico you would see higher rates - but both of these southern states along with Louisiana and Mississippi have low incidence and low death rates.
To me these charts do not scream "Wear Sun Screen 100% of the Time."
The supposition is that both UVA and UVB rays from the sun penetrate the skin and trigger cancerous growths which develop into skin cancer.
Now, buried in the American Melanoma foundation link is an interesting fact: skin cancer on women's torso's ages 15-29 is the fastest increasing incidence rate among all demographics.
One imagines that if the sun were causing this problem it would be common in all southern states. But its not...
On the other hand, one would expect that for women using tanning beds, especially in northern climates where there isn't much sun exposure, too much tanning might be the cause of skin cancer. And give that young female torso's are where the rates are increasing the fastest one has to believe that tanning beds are much more likely the problem.
So what about all this slathering of high SPF crap on your skin?
Well, there are two problems there:
First, you skin is a big source of vitamin D. It creates this vitamin D from sunlight. Without sunlight and other sources of vitamin D you can become deficient.
Slathering high SPF sunscreen all over kids before they go outside denies them vitamin D production - especially in their critical early years.
Some, such as this article, don't believe this to be an issue. I think it probably is, at least for small children who do not get enough vitamin D from other sources.
Second, one has to wonder what is in sunscreen.
Here there is less direct concrete evidence but people are at least questioning the basic idea of slathering unknown chemicals daily on themselves.
To block UV (A or B) sun screens are using chemicals like titanium dioxide or "nano particles."
Titanium dioxide has been around for decades (its the white stuff on the lifeguard's nose at the beach). But today's sunscreens bring this chemical into contact with the entire body. And these particles are small and can enter the blood stream through the skin.
Similarly with "nano particles" (finely ground zinc or titanium dioxide or other chemicals). No one really knows if they can penetrate your skin or what they will do to you if they do (see this).
I think the dogma of stupid rules this area of health care. To me the facts are clear:
1) If you are white skin cancer is a fact of life - be aware of your body and what you skin is doing.
2) Stay out of tanning beds and don't lay burning in the sun.
3) Occasional use of "old fashion" sunscreen is probably okay, e.g., at the beach for a vacation, and to prevent serious burns.
4) Do go out in the sun for a walk or other regular exercise to ensure you get enough vitamin D.
As far as any science is concerned - one thing that has entered our lives since the 1970's has been tanning and tanning salons. Yet I can find no statistics on them.
I wonder if they have anything to do with the increased incidence of cancer on young female torsos...