FAA guidelines:
Summer (May-Oct)
190 Ave
200 male/179 female
child 2-14 82
Winter (Nov-Apr)
195 Ave
205 male/184 female
child 2-14 87
The above weights include a 16# allowance for carry-on plus 5# summer or 10# winter clothes.
30# standard checked bag and 60# ave heavy. Most carriers weigh checked bags and then transmit the figures to dispatch.
IATA should not be far from these figures.