... necessarily mean there's an increase in the number of injuries.

... doesn't equate to an increase in the actual number. What used to be a "sore arm" is now more specifically diagnosed.

Remember, there were zero Tommy John surgeries before Tommy John.

But thanks for your input

but it's not the whole story.

Yes, he is absolutely right about the effects that occur during a kid's younger days. Gone are the Little Leaguer who won because he threw the hardest. That only works in the local league. There isn't a travel team around where pitchers only throw fastballs. They're taught how to throw curves and different types of changeups. To their credit, Little League does now have much stricter policies surrounding pitch counts as opposed to innings which is helping.

It's in the higher levels where the rules differ. It's become more of an innings pitched rather than pitch counts that are the norm. That, I'd like to see changed. If I remember watching MLB network during this year's draft there were at least two of the top pitching prospects drafted who had already had TJ surgery. In the past, this would have scared most teams away. But now, and yes, technology and procedures have allowed doctors to know more about the surgery and the success rates having greatly increased, many teams now see this as less of an issue and are willing to be more aggressive in letting the procedure be done due to the increased benefits.

My nephew played in a town league, and all star team and AAU and while each had an inning limit policy, there didn't seem to be any limit between leagues so it's left to the managers to take that into account. His coaches did a pretty good job of taking it all into account, but I could see where some of the ultra-competitive coaches may not if they have a stud and really want the win.

I wonder if it gets worse for a few reasons:

Guys threw 300 innings and only some guys had arm trouble enough to greatly affect their ability. BUT(!), they were throwing off a much higher mound. If you start higher, your stride into the pitch has to land farther down the mound which means the hips and body have a little more time to square up and drive off the back leg. Also, it might result in the front foot landing a little closer in time to the arm swinging through. So, it's a little less arm tension and the breaking stuff isn't going across the body as much.

Second thing: Every coach thinks they can teach control so a guy with decent movement who could throw a golf ball into a soup can is ignored unless he can throw 95. Hence, young kids with potential work too hard on throwing harder and harder before their soft tissue is ready, lifting weights to get stronger but still not having the ligaments and tendons to handle the strain, and not learning to "pitch". They just learn to throw.

Third thing: I'm old enough to remember a LOT of great pitchers in the 60's and 70's. One thing is see as different (generally, not universal) is the leg kick is lower than back in the day. Koufax, Marichal, Drysdale, Gibson, Jenkins, Seaver, Ryan, et al all had leg kicks where the leading knee was getting up to the letters. I find it weird in the "moneyball" era where stealing is discouraged, that we have guys low kicking to keep runners on, when mostly they don't steal bases anyway. Does the lower leg kick result in more mechanical issues that strain the arm?

I buy the year round thing in the article. That makes sense as their isn't enough downtime for longer term repair to take place.

Not saying i've figured it out. Just some observations that seem to make some sense.
But, i wonder if the lower mound hasn't affected how the typical pitcher throws

but just like CTE (Chronic Traumatic Encephalopathy) in football, I'm going to suspect the stage was set in youth programs.

According to the link, Selig has commissioned a study.

Still, i'm stuck on what would have happened, even given the youth programs, if they were throwing off the 18" mound.

Officially it was 15 inches until it was lowered to 10 inches in 1968 following the "Year of the Pitcher."

Some teams did cheat with a higher mound -- especially those who had very good pitching. The Cleveland mound, according to the then groundskeeper, was 19 inches, because "Bob Feller like to ride high." It was rumored that the Dodger mound was sometimes as high as 20 inches in the 1960s.