Jim Smith,

Wear of the pins and holes is certainly cumuilative although chain stretch is a bad description, better is chain elongation.

If each pin and each pin hole were to wear .001 inch where they touch each other, chain each link would be offset by .002 inch from new. Thus the overall measured length will be the original chain length plus .002 inch times the number of links.

If you compared a new chain to a worn one, you would see a definite difference in length. Also the arc of a worn chain would be greater due to the "slop" between the pins and holes.

P E H