Over/Under Elimination Games

I'm not even sure where I heard this from (maybe ESPN's Chad Millman) that NBA elimination games tend to go under.'

Soooooo, I went back a few years and got these numbers.

               O-U
2006-07: 11-10
2007-08:  7-15
2008-09:  9-13
2009-10:  7-14

That's a total of 14.6 units (assuming a -110 line).

The reason I post this, is to 1) contribute to the systems forum
                                         2) see if anyone can backtrack further
                                         3) to see if any filters can be added

Are Game 6's and 7's more likely to go under cuz both teams have taken at least 1 game from the other?

Should we stay away from high scoring teams?

I looked round by round these 4 years and couldn't spot a trend for any particular round of the playoffs.

Also, could this theory, if applicable to NBA, be useful for NHL or WNBA?