According to industry reports, guitar sales have decreased consistently for over a decade. Total US guitar sales dropped over 50% from 1.5 million units yearly in the 2000s down to around 600,000 as of 2020.
However, the past few years showed a leveling off of declines, and 2021 even saw a slight uptick likely driven by pandemic factors. But regardless, the market has gotten undeniably smaller since its peak.
That doesn't have a breakdown as to age of buyers, but if sales are less than half what they were two decades ago, I imagine that playing the guitar is probably less popular than it was at that point in time.
It does seem unlikely that, regardless of interest in playing the instrument, sales would’ve done anything but slumped in recent decades. Can’t really envision buying brand new guitars being a high priority for young people who are seemingly worse and worse off over time
Their data mentions the demographics of people who play guitar, not just those who buy them. (In 2022) 18-34 are about 40% of guitar players with the largest share. Boomers also still play but don't exert market influence.
That actually sounds like Gen X are the smaller guitar playing demographic, maybe? Could just be too busy with careers.