Does there exist a chart documenting the number of bitcoin merchants over time, and if not, would it be possible to create one from any available data source? (I'm thinking mostly of https://en.bitcoin.it/wiki/Trade for source material)
I went through the last 500 revisions of the wiki page, pulled the byte count into excel and graphed it. Line count would probably be a better metric but I didn't have a readily available data source for that. If someone wants to write a script that wget's each revision and counts the number of
tags that might be more accurate, but here's 500 revisions worth of data as a chart:
500 revisions goes back to Jul 8, 2011.
Also of interest, the earliest revision (Feb 10, 2011) of the Trade page has a scant 117
<li> tags while the current page has a whopping 785! I haven't taken the time to count all the revisions inbetween but that's quite a lot of growth - 668 new entries in 225 days for an average of almost 3 entries per day or about 1,084 per year! While some of these are bound to be non-merchant list items, that's still an impressive rate of growth.
I have not seen a chart. The only way I think it would be to go through the history of the wiki page and count the merchants at certain dates to get the data.