There is a fundamental flaw in your analysis.  Yes, home teams win 54% of the time --- in the regular season.  But we're talking about the World Series now.  The HFA is much greater in the postseason, and especially in the World Series.  There are many reasons for this, including familiarity with the park and the designated hitter.  

But the biggest reason is one you alluded to yourself: "assuming the two teams are equally matched".  In the regular season the majority of games involve teams that are NOT evenly matched.  There is usually a clear favorite, independent of HFA.  That tends to dilute the importance of the HFA.  The Yankees should beat the D'Rays most of the time, wherever they play.  In the playoffs and WS the teams are more evenly matched, so any edge gets magnified in importance.  Run your analysis again using playoff and WS data and I'm sure you'll come to a different conclusion.

This article is good

http://www.washingtontimes.com/sports/20060713-121440-6690r.htm

The author, Dan Daly, said

"from 1965 to 1972, the club with the home-field advantage lost eight straight World Series. And some of these, I'll just point out, were pretty fair clubs -- the Earl Weaver Orioles (twice), the Sparky Anderson Reds (twice), the Sandy Koufax Dodgers, the Bob Gibson Cardinals. And get this: From 1955 to 1975, the club with the HFA lost 17 of 21 Series -- nearly the exact opposite of the current streak."

 

I looked at all World Series games back to 1980. Combined H-R record: 86-55, 61%.  Here it is by decade:
1980's 36-22 62%
1990's 28-22 56%
2000's 22-11 67%
As I was compiling this, I noticed there were 5 4-game sweeps.  4 of them went to the team with the HFA.  Together, those games add up to 10-10.  Take them out and the remaining games were 76-45, 63%.  Also, there were seven 7-gamers. One was 2-5, two were 3-4, one was 5-2 and three were 7-0.  That's 34-15, 69%.

I think we have to look at all post season games since, if I understand your theory correctly, is that the teams are evenly matched. That would tend to be true in LCS games, too. So why not count them? Unless there is something fundamentally different about the WS compared to the LCS.

Also, as Dan Daly pointed out, there was a period where the team with the HFA did poorly. Is there some particular reason why it changed? I think in the 70s, the team with HFA won only 3 of the series.

I used those win/loss totals for the 80s through now and got a cumulative pct of .610 for home games.

Plugging that into my tables, I get that the team with the HFA will win 54.3% of the series.

I think that is still not too big. And that is based on the extreme level of HFA.

It would mean 1 additional win about every 12 years.

Now I may not be looking at that the right way. In the original article, I said that the team with the HFA gets an extra 30 wins. But maybe I should have said 15 since if you win 51.5% of the series, in 1000 years you win 515 times. If the two teams were even, then you expect an even 500 wins, and 515 mean an additional wins.

So here, with a .543 pct, it means 43 more wins. That is 1 more win every 23 years or so for the team with the HFA.

If one team wins 6 out of every 11 series, that is a .545 pct.

Here is another way to look at it. If two evenly matched teams played the world series 22 times, but team A always had the HFA while team B did not, team A would win 12 times, while team B would win 10 times. So 1 more win every 22 years for the team with the HFA.

12/22 = .545

My theory is that HFA is moderately higher in the playoffs but it is much higher in the World Series.  As I said in my original post, that's because of things like lack of familiarity with the ballpark and the designated hitter.  The fan frenzy element contributes too.  I think you need to calculate HFA's separately for the playoffs and the WS.

Just heard on ESPN that the home team has won the last EIGHT WS Game 7's!

I went back and double-checked my figures.  I found one game I missed completely the first time (a Game 7 win for the home team) and one game that I counted as a home loss which was actually a home win.  So the revised figures are now 88-54 or 62%.  Pretty strong evidence, if you ask me.

In the process I uncovered something that even I find surprising.  If you look only at games where the HFA team is actually at home, the effect is much stronger.  The HFA teams were 53-20 (73%) at home.  On the road they were 34-35 (49%).  In other words, the teams that have to start the Series on the road have almost no home field advantage even when they do go home for games 3, 4 and 5!

It's also interesting to look at how the HFA team fared game-by-game.

HFA Team at Home
Game 1 16-9 64%
Game 2 18-7 72%
Game 6 11-4 73%
Game 7  8-0 100%

HFA Team on the Road
Game 3 14-11 56%
Game 4 12-13 48%
Game 5  8-11  42%

The HFA Team's advantage at home increases as it gets later in the Series.  Meanwhile, the only game where the other team has a clear-cut advantage is Game 5!