Was having an interesting conversation with a friend during a long stopover. A point came up: What percentage of tickets are typically sold on an airline's own website versus all the other channels (e.g. Expedia, Travel Agents, other airline ticketing etc.)?

Of course, the figure must vary a lot but just wondering about approximate estimates.

Also, when one buys from say, Expedia or a similar site: Is the logistics analogous to buying from a travel agent. In the sense, at the back-end does Expedia still just issue a request into the same booking pool that a Travel Agent terminal does?

Or do these large websites get access to a dedicated pool of tickets etc.?