Funny how even the driest of magazines finds a way to bring in the celebrity-obsessed reader. Portfolio's Duff McDonald makes a heroic effort to calculate the size of the Britney Spears economy. Record companies, paparazzi photographers, celebrity tabloids, and her estranged husband Kevin Federline: they all feed off the public's fascination with the popstar's rise, and fall. The pie chart shows the breakdown. One great data point: photo agency X17, which has paps working in round-the-clock shifts to ensure it doesn't miss a meltdown, garners 30% of its income from the troubled Spears.