I was a bit surprised to find that the average recorded atmospheric pressures at such locations as Mexico City (2.2 km above sea level) are roughly equivalent to those *at* sea level, i.e. in the 99-102 kPa range. I find this a bit odd, since the air density at this location is just under 80% that of sea level. So, one would expect the barometric pressure to be correspondingly lower as well. Are there any atmospheric physicists who can help shed light on this conundrum?