I'm going to leah a little inside information I've obtained from a guy I know, which the last Few sets has seemed to yet be proven wrong.
All products are more EX and "Shiny" populated the few month or two of the set being released.
Then as the set dies down the pull rates go down just a little bit.
Out of a combined 12 booster boxes. (6 in the first month, 6 in the last month or so up until today).
The first six ALL came with at least 4 EX(2 FA 2 REG) and 1 Secret. The last 6 have all been 3 EX (1FA 2 REG) and 1 secret (1 of these boxes didn't have a secret at all.
I don't think this is a coincidence at all. It's an economics type of thing if you think about it.