3.3 Controls
We controlled for a broad array of variables that may affect CHRO presence but are beyond the scope of this study. We included the year variable (ranging from 1998 to 2007) to control for time trends (Hambrick and Cannella, 2004). We controlled for firm size, as measured by the logarithm of the number of employees. We also included prior performance (t − 1) to control for CHRO appointments that were due to good (or bad) performance. Prior performance was measured by the return on assets (ROA), market-to-book value (MTB), and prior sales growth. Data were collected from S&P’s Compustat.