All these percentages are basically meaningless. There have been such drastic changes in the denominators (Total World Manufacturing and US GDP) used to generate these percentages that the resulting percentages mean little.
For percentage comparisons to be meaningful, the denominator must have remained fairly consistent as to the ratios of the various elements which make up the denominator. The elements of these denominators has changed drastically over 60 or more years. Ex. the US had its first $100 billion budget under Kennedy. It’s now $3 trillion plus.
It would take a lot more analysis than a simple division of one element of GDP by total GDP to yield meaningful percentages because the denominators have changed so much.
Are there any numbers you like?
You have any data on these changes? Are you talking about products that are now counted as manufacturing that once were counted as something else?