One sure sign of competitive balance is this: Nobody remains at the top year after year. In fact, Major League Baseball is 0-for-the-millennium in the category of back-to-back World Series champions.
This is a long way from the Yankees' five straight titles from 1949-53 -- the beginning of a remarkable run of nine World Series championships over 14 years.
It is also a long way from the Oakland Athletics winning three straight from 1972-74. And it isn't close to the most recent Yankees run of domination, winning four out of five from 1996-2000, including the last three in a row. This was also the most recent time the word "dynasty" was tossed about in baseball circles.
The defending champion Kansas City Royals are currently on the outskirts of the American League Wild Card race. Nobody who has watched the Royals over the past two years would count them out prior to an official elimination.
But at this point, the Royals' chances for a repeat World Series championship are seriously slim. The structure of the current game is not inclined toward repeat champions. It is intended to give more teams a chance to win; more fans a chance for legitimate hope. It is working.
What has happened to the 15 World Series winners of the new century? It wasn't all bad by any definition. But it also wasn't back-to-back glory.
2001 D-backs: This veteran club wasn't necessarily built for the long haul, but it was brilliant enough behind Randy Johnson and Curt Schilling to end the Yankees' run of domination in a thrilling seven-game World Series. The D-backs were swept in 2002 by the Cardinals in a National League Division Series.

2002 Angels:They prevailed in the World Series over the Giants in what was a battle of Wild Card qualifiers, another seven-game drama. They skidded to a sub-.500 third-place finish in 2003.
2003 Marlins: The NL Wild Card representative made it past the Cubs in an infamous seven-game NL Championship Series before upending the Yankees in six games in the Fall Classic. What followed was an 83-79 mark and a third-place finish in 2004.
2004 Red Sox: Technically, they ended an 86-year championship drought with a four-game sweep of the Cardinals. But a mountain had already been climbed when they came back from a three-game deficit to beat the Yankees in the AL Championship Series. In 2005, Boston was swept in a Division Series by the White Sox.

2005 White Sox: They recorded their first championship in 88 years with a dominant performance, going 11-1 in the postseason. In 2006, the Pale Hose won 90 games but slipped to third in the AL Central.
2006 Cardinals: This club won 205 games over the previous two seasons, but it was a mere 83-78 before rolling to this championship. The Redbirds fell to third place and a sub-.500 record in 2007.
2007 Red Sox: Josh Beckett was dominant and so were the Red Sox, sweeping the Rockies in the Fall Classic. They lost the next year in the AL Championship Series to the Rays, a team making a breakthrough of historic proportions.
2008 Phillies: The Rays' magic didn't work on the Phils, who received a dominant postseason from Cole Hamels and won the Fall Classic in five games. The Phillies got to the doorstep of a repeat in the '09 World Series but lost to the Yankees in six.
2009 Yankees: They were back on top with a convincing performance, losing only four games in three postseason series. But this was no dynasty in the making. The Yanks lost the next year in the ALCS to the Rangers, and they have not been back to the World Series since.
2010 Giants: This was the start of a remarkable run of postseason success that resulted in three World Series championships over five seasons for the Giants. In the contemporary game, that's as close as anybody has been recently to postseason domination. But the back-to-back championship has eluded them. In '11, the Giants were a distant second in the NL West.
2011 Cardinals: They went all the way, once again as a Wild Card team. The Cardinals have been consistent, making postseason appearances in the past five seasons. But in '12, they lost to the Giants in a seven-game NL Championship Series.
2012 Giants: They swept the Tigers in the World Series for their second championship in three seasons. But in '13, San Francisco wasn't close, finishing in a tie for third in the NL West at 76-86.

2013 Red Sox: What a ride. The Red Sox went worst to first from 2012 to '13 with a remarkable 28-game improvement, culminating with a six-game victory over the Cardinals in the World Series. But Boston encored with a 26-game regression and another last-place finish in the AL East.
2014 Giants: Another even-numbered year, another title for the Giants with a taut, tense seven-game Series, this one against the Royals, featuring the brilliant pitching of Madison Bumgarner. But in '15, the Giants finished eight games back of the Dodgers in the NL West. What about now, another even-numbered season? As we speak, the Giants are tied for the second NL Wild Card spot with the Cardinals.
2015 Royals: After winning the AL pennant in 2014, Kansas City won its first World Series in 30 years with a refreshing combination of a lockdown bullpen and an offense that relentlessly put the ball in play. Now, with 12 games left in the regular season, the Royals are five games out of the second AL Wild Card spot. They typically do their best work coming from behind, but this looks like yet another example of how hard it is for a team to repeat in contemporary baseball.