For an unnamed European airlines --
Total mileage members - ~2.6mil
General member - ~2.3mil
Elite tier 1 - ~250,000
Elite tier 2 - ~60,000
Top tier - ~15,000
So in this case about 12% of members are some form of elite.
Ultimately a well proportioned program will look like a pyramid. Wide base with tons of general members, narrowing as one moves up in the elite levels till reaching the top level which will be a very small percentage of elites.
Many say AAdvantage last year rewrote its lifetime elite level earnings method as it was getting too heavy at the higher levels.
From the desert to the sea, to all of Southern California