We've been hearing about the Eastern Conference's poor performance for years. Now, thanks to some data from Basketball-Reference, we can pinpoint the beginnings of the Leastern Conference.

On Thursday, Neil Paine wrote a blog post for Sports Reference that included the wins of the two NBA conferences by year. Data is nice, but looking at a table of numbers isn't the easiest way to analyze data. I've taken that data and turned it into a few simple charts.

The chart above shows the winning percentage of Eastern conference teams since 1951. The red line represents the winning percentage of Eastern Conference teams during the regular season, while the blue line represents the East's winning percentage in games played against Western Conference teams. It also shows us that the East has been the Least since the 1999-2000 season. During that period, the East has approached a 50% record in interconference games only once, in 2008-09, when it won 51.3%. And actually, the East hasn't been doing too well since 1989-90; over those 25 seasons, the East has only had a winning record against the West six times (92-93, 95-96 to 98-99, and 08-09).

But in the seasons before that, the East typically beat the West, with the West only managing to win the head-to-heads in 10 of those 39 seasons. In fact, right before the rise of the Leastern Conference, the East had run off 10 straight years above 50% (from 1979-80 to 1988-89). And from 1954-55 to 1969-70, the East strung together 16 consecutive years above 50%. So, before the East was the Least, it was the Beast.

Here's that same chart, but flipped to represent things from the Western Conference perspective:

With only two conferences, the East's loss is the West's gain. If the first chart was named "the decline of the East', this one would be named "the rise of the West". This year, the Western conference is threatening to break the record for the best head-to-head record. The West is at 70.8% in interconference games, and the closest either conference has been to that mark is when the East won...70.8% of its in 1959-60. Back then, the NBA only had eight teams, and the "western" teams were St. Louis, Detroit, Minneapolis, and Cinncinati.

What the West is doing this year is far more impressive given the increased size of the league. The highest mark by either conference in the modern era (and second highest overall) was in 2003-04, when the West won 63.3% of the interconference games. That year only six Eastern teams hit 0.500: the Pacers (61 wins), the Pistons (54), the Nets (47), the Heat (42), the Hornets (41), and the Bucks (41). In the West, only four teams didn't hit 0.500: the Warriors (37), the Sonics (37), the Suns (29), and the Clippers (28). The Jazz won 42 games and finished 9th in the West; if they had been in the East they would have tied with the Heat for 4th place and homecourt advantage in the first round.

This season seems to be shaping up in a similar fashion. The East only has three teams at or above 0.500: the Pacers (17-2), the Heat (14-4), and the Hawks (10-10). The West only has three teams under 0.500: the Timberwolves (9-10), the Jazz (4-16), and the Kings (4-12). In 13th place in the West, the Timberwolves would be fighting for 3rd and 4th place in the East. It's even worse if we look at point differential. The Pacers and the Heat are the only two Eastern teams with a positive point differential; on the other hand, the Grizzlies, the Lakers, the Kings, and the Jazz are the only Western teams with negative point differentials.

We've only reached the beginning of December, so this story could certainly change by the end of the season. But the East's performance has been so bad that it's hard to imagine much of an improvement.

If 2003-04 repeats itself this year, that will be the second time in 11 seasons. Perhaps the NBA will take a harder look at seeding playoff teams based on record alone, or adopt some version of the crossover rule?