Making Sense Of Contradicting Lines

Last week, Results Disoriented's "j holz" had a very interesting post about the discrepancy between the Red Sox-Rockies series line, and the individual World Series game lines. I'll let him elaborate:

"Indeed, the Series line closed at a market price of roughly Rockies
+210/Red Sox -210. For those of you not familiar with money lines, that means
the Rockies are expected to win the World Series 100 / (210 + 100) = 32.3% of
the time.

"Given these individual game percentages, we can calculate the chances of
the Rockies winning the Series--using the same method I did to come up with my pre-WS estimate. It comes to...24.9%."

He goes into much more detail in his post, but that's the basic idea. There are two theoretical reasons that cause this discrepancy. One is that individual game lines attract both more action, and more intelligent action. "Homers" who just bet on the team they're rooting for, make up a decent portion of the action on the World Series line.

The second, and probably more relevant factor, is "momentum". I think the general consensus among "statheads" is that the idea of momentum in baseball (or any other sport, really) on a game to game basis is kind of silly. You don't have a better chance of winning today becuase you won yesterday; the only thing that matters is how good you are today.

Well, the Rockies came into the World Series with about as much momentum as you can possibly have, having won 21 of 22. It seems like Vegas took advantage of the misconception that this was going to give them a chance against a clearly superior Red Sox team. Even so, the line was -210, which really shows just how superior the Sox were.

These two factors allowed the oddsmakers to get away with a seemingly unreasonable line, because they knew they would get sufficient action on Colorado at +210. I suppose that if Colorado had somehow beaten Josh Beckett in G1, the lines would have continued to reflect the "momentum" that the Rockies had.

Well, they didn't (I guess you could argue that they ran into Beckett's "momentum"...or something), and the lines for the rest of the series (COL was +190, +130, +130 in Games 2-4, respectively) reflected Boston's superiority. So it seems like the people making the lines knew they would get plenty of action on the Rockies, even though the linesmakers themselves thought betting in Colorado at +210 was a poor idea.

While I'm at it, I'd like to look at the Patriots lines again. Let's compare their Week 6 game in Dallas, and Sunday's game in Indy.

NE (-5) @ DAL
NE (-6) @ IND

If you assume the Patriots were as good in Week 6 as they were in Week 9, these lines indicate that the Cowboys are one point better than the Colts. This, of course, is completely unreasonable. If those two teams played on a neutral field tomorrow, the Colts would be significantly favored, probably by 5 or 6 points.

Clearly, there's something else going on here. Part of it is that the Pats beat Dallas by 21 (although they were only up 4 at the half). But I think the bigger factor is this:

New England 52, Washington 7

Did those four second half TDs that New England scored to increase a 24-0 halftime lead into a 52-0 fourth quarter lead make the Pats a better team? Doubtful. But did it make them seem like a better team? Apparently so, given the inflated line on Sunday. It made the Pats seem invincible, to the point that they could be favored by as much as 6.5 points against the Colts in the RCA Dome.