Intuitively, a scorer who serves as the clear focal point of his team's offense ought to have a lower scoring efficiency than he would have were he able to shift into a more secondary role. Playing alongside other skilled scorers should, in short, open up more opportunities for quality shots. Ray Allen seems like a good candidate for this effect, going in one offseason from being the first option in Seattle to having the third-highest usage rate on the Celtics where Kevin Garnett and Paul Pierce share the load.
As you can see, it hasn't happened. His usage rate is lower "true shooting percentage" (a figure that takes into account free throws and the fact that three pointers are worth three points) than during his Seattle days, but his TS% is nothing special -- lower than it was last season, which, in turn, is lower than it was the season before. But perhaps it's just the effect of aging. Kevin Garnett's usage rate is at its lowest point since the 1997-1998 season and he's posting a career-high TS%.