[Mick]

That certainly makes sense if you compare the 1964 Olymp LJ with 1968.  The top 16 jumpers in Tokyo in 1964 had an average top mark of 7.656 meters.  The average in Mexico City was 7.96 for a disparity of .3633 meter per average top mark, which indicates that Olympic level jumpers could expect to jump 14 19/64" further at altitude than at sea level.

But if you compare the averages of the top 16 jumpers at the 72 olympics with those from the 68 olympics, the disparity is much narrower.  As noted, the top 16 from Mexico City jumped 7.9606 whereas the top 16 from the 1972 Munich Olympics jumped an average of 7.9256 meters, making the difference between top 16 marks just 1 3/8" which is negligible.

[Mick]

That certainly makes sense if you compare the 1964 Olymp LJ with 1968.  The top 16 jumpers in Tokyo in 1964 had an average top mark of 7.656 meters.  The average in Mexico City was 7.96 for a disparity of .3633 meter per average top mark, which indicates that Olympic level jumpers could expect to jump 14 19/64" further at altitude than at sea level.

But if you compare the averages of the top 16 jumpers at the 72 olympics with those from the 68 olympics, the disparity is much narrower.  As noted, the top 16 from Mexico City jumped 7.9606 whereas the top 16 from the 1972 Munich Olympics jumped an average of 7.9256 meters, making the difference between top 16 marks just 1 3/8" which is negligible.