I haven't kept very good records of QSLs sent, so don't have a good feel
for the return rate (I still have a pretty good-sized pile which I need to
send to the buro), but have noticed that more stations seem to be using
LOTW and I now have an 18% return rate there (779/4294), although I
haven't yet entered anything for QSOs prior to 2000. TI9M showed up on
LOTW just today.

73, Bob N7XY