You might not have noticed it, but the 2012 Philadelphia 76ers are quietly having one of the greatest defensive seasons of all time. They currently lead the league with the fewest points allowed per game (88.2) and, more importantly, per 100 possessions (98.0). If they can hold off Boston in the latter category for another three weeks, they'll have accomplished a feat only nine teams since 1986 can claim -- leading the NBA in defensive efficiency wire-to-wire.
Moreover, their defensive rating of 98.0 is the lowest any team has posted in the last eight seasons. Although the league as a whole has declined in points per possession during this lockout-shortened season, Philly's D has been historically great in terms of efficiency allowed relative to the league average. Using a simple method of estimating pace factor for teams prior to 1974, we determined that the 2012 Sixers rank 22nd among the best defensive NBA teams since 1951.