Are there an applicable numbers that you can provide as being "valid to generate stats from denominators whose makeup has changed significantly over the time period used" or have you rejected all statistician and mathematician stats?
I’m not the one who introduced this topic and drew conclusions from very scant data. And why did you start the US % of world manufacturing in 1995?
An interesting stat would be dollar value of mfg. goods sold in the US compared to dollar value of mfg. goods produced in the US over several decades.
A big factor in these comparisons is that there are so many more products being produced now that didn’t even exist twenty and more years ago. How much has total mfg. grown worldwide and in the US over the decades? Mfg. as percentage of GDP doesn’t tell us very much.