From what I've been looking at (tho this is still at the level of impressions, not of statistical data), the best single correlation to frequency seems to be the size of the smallest distinct precedessor. Assume clouds of activity that will randomly grow, shrink or split: small specific patterns are more likely to be extruded than large, and these will then do some final development into ash.
Achim F's results list does include numbers on smallest precedessors, but I don't see anywhere in there what these precedessors actually are. And in a few cases, it seems the pattern itself is counted rather than a distinct one.
Size is another factor as well. Once formed, a pulsar will obviously be more likely to be destroyed by a lingering reaction than, say, a longboat. However I'm not sure how exactly to quantize this. Surface area seems more relevant than density; another question is how to handle eating reactions in this context.
This model doesn't entirely work due to small methuselahs, however. I saw it noted in another topic that Herschels escaping near edges are the most common origin of ships from small seeds; similarly, I wonder how much of a contribution eg. centuries colliding with other junk have on the toad production frequency.
In more general, I would find it interesting to analyze what are the typical origins for any given object. For example, blinkers seem to mostly result from traffic lights, with a secondary contribution from these patterns I might call "blinkinserter 1" and "blinkinserter 2":
Code: Select all
..O.. .OOO.
OO.OO O...O
.O.O. OOOOO
..O..Some patterns can also quite well emerge from chaos fully formed; this seems to be the case especially for snakes and *WSSes, which don't really have any considerably small precedessors. Blinkers and gliders do this commonly as well, but it seems that patterns with a width of more than 2 are rare to see form in this fashion. Which makes sense: clouds splitting usually involves a central overpopulated zone dying away, with only some edge cells and their possible descendants surviving.
Also it still has me stumped why pentadecathlons are as rare as they are. Pulsars have a handful of 7-cell precedessors, and yet they are almost 100 times more common. PDs have at least 144 possible 8-cell ancestors (from 2 traffic lights) which does not look that much worse. Is this then because two active components are required? I dunno; but maybe we could find out if we had some general stats here. FWIW, I've seen a natural PD occur twice (outside of mirror axes); one was indeed a 2-TL collision, the other a queen-bee-on-blinker reaction.