Say I have built the WebRTC video chat website, some connections after the handshake (ICE Candidates) will go directly p2p, some will use the STUN server, and some will use the "last resort" the TURN server to establish the connection. TURN server based connection is very expensive compared to the direct connection and the STUN connection (which are free) because all traffic must actually go through the TURN server.
How can we estimate the percentage of connections of random users that will need to to go via TURN? Imagine we know very little about the expected audience, except that the majority is in the US. I believe it must be difficult to figure, but my current estimation is somewhere beween 1% and 99%, which is just too wide, can this at least be narrowed down?