Interesting stuff from the New York Times’ David Leonhardt and Ford Fessenden, though it should be said that if you take Tim Floyd’s term with the Bulls out of the mix….the numbers are even worse.

The men coaching N.B.A. teams in recent seasons have looked like no other group of head coaches in the history of major American professional sports. Today, 10 of the league’s 30 coaches are black, ranging from young former players like Terry Porter in Milwaukee to veterans of multiple coaching jobs like Bernie Bickerstaff in Charlotte.

At a time when the National Football League can count only 10 black head coaches in its history, the National Basketball Association has reached a position rare for any business: when a black coach or executive is hired or fired, almost nobody mentions race. Opportunity in the N.B.A. appears to have become color blind.

But the coaches who have received those opportunities have not had much time to enjoy them. In a pattern that has gone largely unnoticed, except among black coaches themselves, white coaches have been holding on to their jobs for significantly longer than black coaches. Yesterday, the Cleveland Cavaliers fired Paul Silas, who was in his second season with the team.

Over the last decade, black N.B.A. coaches have lasted an average of just 1.6 seasons, compared with 2.4 seasons for white coaches, according to a review of coaching records by The New York Times. That means the typical white coach lasts almost 50 percent longer and has most of an extra season to prove himself.

This month alone, three of the six black coaches who had held their jobs for more than a season have been fired, including Silas, who had eight years of N.B.A coaching experience before joining Cleveland. The Orlando Magic dismissed Johnny Davis last Thursday after less than two seasons. On March 2, the Portland Trail Blazers fired Maurice Cheeks, then the black coach with the second-longest tenure; he had lasted almost four seasons.

“Our white counterparts are given more the benefit of the doubt,” Silas said in an interview in January. “Things have changed dramatically in our society, but it still has a long way to go.”

The gap has created a deep division among coaches and executives, one that splits largely but not exclusively along racial lines. Some, including Commissioner David Stern, said the numbers surprised them and called them largely a coincidence. Doc Rivers, the coach of the Boston Celtics, who is black, said he thought that owners and general managers now gave white and black coaches equal chances to succeed.

“Does race have anything to do with this? Now I’m sure the people who do the hiring say no,” said Al Attles, an assistant general manager of the Golden State Warriors, who in 1969 became the third black coach in N.B.A. history and later won a championship. “But it surely has to be something more than wins and losses. If it walks like a duck and quacks like a duck, eventually you have to say it’s a duck.”

Even if the cause was rarely conscious racism, coaches said, age-old athletic stereotypes – the black athlete as a prodigal talent and white athlete as hard-working gym rat – can make blacks seem particularly unsuited to be good teachers. Some black coaches said they thought that team owners and general managers, a largely white group, were probably most at ease with people similar to them, just as most people were.

And players, both black and white, are still far more accustomed to seeing whites in positions of authority than blacks, coaches said. Some black coaches, including Cheeks in Portland and Byron Scott with the Nets, lost their jobs after clashing with a black player.

The N.B.A. coach with the longest tenure today is Jerry Sloan, who is white and is in his 17th season as coach of the Utah Jazz. The calculations of average tenures by The Times included only coaches whose tenures had ended. But when Sloan and other active coaches were included, the gap between white and black coaches was nearly identical.

To many white executives, the lack of a clear connection between race and individual firings makes the pattern seem all the more likely to be a coincidence.

“My general feeling is that it’s a performance league, and there is equality in it in that sense,” said Donnie Walsh, the chief executive of the Indiana Pacers. “If you do well, you’re going to move on to a better job or another job. Those that aren’t performing are going to get fired.”

“For black coaches, you have to be a Jesus miracle worker,” said Butch Beard, who was fired after two disappointing years with the Nets in the mid-1990’s and is now the head coach at Morgan State. “With a bad team, ownership wants you to do more than what the team is capable of doing. If you don’t pull it off right away, they think it is the coach’s fault.”

Beard added: “This won’t get me another job, but that’s the truth. It’s very disturbing to me.”