Edit: please disregard the rest of this post. Incorrect math was used in the calculations. They are all incorrect.
Everyone loves parlays. The reasoning is simple. Smaller risk for a bigger return. It sounds great in theory, especially if you like both the side and total in a game... Here's some simple math that made me stop betting parlays, with the exception of an occasional highly - correlated 2-teamer.
Everyone knows that 52.38% is the break even point at -110. If you flat bet, any percent above that is profit.
The following math assumes 13/5 payout for 2-team, 5-1 for 3 and 10-1 for 4.
The break even points for 2 team parlays is 62%. A 3 teamer is 58.5%. And for a 4 teamer, it's a little over 56.2%.
Another way to look at it is, let's say you can hit 56.2%. You're good enough to almost break even long term betting only 4 team parlays. Over the course of 1000 bets of $100, here's your expected return:
2 tm: $-17,880
3 tm: $-11,247
4 tm: $-242
Strait bets: $8,020
Even if you get a little better returns on parlays than that, you still have to win a higher percentage with parlays to break even long term.
You can keep your occasional big wins, I'll take the long term profit every time.