It is taken for granted in the knowledge economy that companies must employ the most talented performers to compete and succeed. Many firms try to buy stars by luring them away from competitors. But Boris Groysberg shows what an uncertain and disastrous practice this can be. After examining the careers of more than a thousand star analysts at Wall Street investment banks, and conducting more than two hundred frank interviews, Groysberg comes to a striking conclusion: star analysts who change firms suffer an immediate and lasting decline in performance. Their earlier excellence appears to have.