The data sources are primarily the Millennium Concordance by Tony Ring, his introductions to Plum Stones, Dan Garrison's Who's Who in Wodehouse, and Jasen's PGW: A Portrait of a Master; I've added some research of my own, and have caught a few typographical errors in each. I'm sure I've added a few errors of my own inadvertently, and don't make any claims that this is the sum of all knowledge on the topic.
One of the advantages of doing this in HTML tables is that I can show (in the few cases where I have information) how the various magazine versions relate to the book versions. For instance, "Rough-Hew Them How We Will" appeared both in the Strand and in Cosmopolitan in slightly differing versions. The Strand version is essentially the one in The Man Upstairs; the Cosmopolitan one has not been collected.
As you'll see, in most cases I have not yet examined the stories to make these fine distinctions, so I would be grateful for brief particulars thereon, as well as any comments, corrections or additions on any point. Send them by e-mail.
Even in its current state, it puts together data that as far as I know cannot be found in any other single place. I hope you'll find it helpful, as I have found the process of compiling it enjoyable. Thanks especially to Tony Ring for checking some of the discrepancies against his original sources.