[tor-relays] How to determine demand/need for bridges/PT?

[Steve Snyder]

Looking at the Tor Metrics page, I can see the number of bridges and the 
number of users connecting via bridges, but that's not enough 
information to determine satisfaction of demand.

Are there now enough bridges to comfortably satisfy demand?  Enough 
bridges with a particular PT type?  If not, what kind of resources are 
lacking?

How does one determine where the need for more bridges, or PT type, is 
greatest?  (Assuming that there is any unmet need at all.)