BaconLover
I've done a lot of analysis on my own wagers but not on overall industry patterns.
The biggest complication is rebates.
This game we play has been getting tougher and tougher to turn a profit because :
1. the lack of new 'dumb' money and
2. the widespread use of computer board watching and data analysis.
Profit margins are so thin that without good rebates you're cooked.
Pools with high take-outs can be in play with rebates and tend to attract less 'sophisticated' players.
My own betting is on Pick 3's - Exactas - 20¢ Supers, in that order.
Superfecta returns depend on a few big hits so they're more of a throw-away type bet.
Your pick 4 comments are spot-on and apply to the pic3s as well.
Of all the ways I've looked at Pic3's the best pattern I've found is to single the leg with the horse that has your lowest line < 5/2 and use no more than 4 picks in the other 2 legs (Max 16 combo's)
“Freakonomics” might be there but impossible to uncover.
Best of Luck with your plays...