I think for new GS members three year mean is pulled down by year -2:

2016 $5000 -$15000
2017 $50000
2018 $50000

When one renews GS, the low first year drops off and the mean should be pulled up. For me and others getting GS was the result of a huge uptick in the type of travel we were doing, and as a consequence, I consolidated travel on UA because of the GS benefits, and increasing the chance of future renewals.

For new members (Like AugustusM) it may be more illuminating to look at the low end of the 2-year mean to see if there is a threshhold. For me, my two years GS-1 and GS Qual were $45000 and $36000. I fell into the AugustusM experience where a decent high year wasnt enough on its own, but two year spend of $80000 clearly was (from IAD, anyway).

T