Being an HR manager on a day to day basis is not unlike hosting a dinner party serving a 5 course meal. So many things to do! Appetizer, Soup, Salad, Entrée, Dessert! You don't have the time to make every course a gourmet, from scratch course. So you have a choice - either make it yourself and cut some corners, or buy take-out from a local restaurant that you know and trust to have great food. If you had more time or more people helping, you could do it (you know how), but that's just not the case. And this meal is important.
Once upon a time, not so long ago, in a land not very far away, there lived an HR manager who was searching for THE perfect candidate. She read dozens of resumes, made numerous phone calls and conducted plenty of interviews. But no matter how hard she tried (in her limited time allotted for recruiting) she never found perfection. She came across bits of it here and there - a perfect degree, a perfect prior job, a perfect title - but never a complete perfect candidate.
Every team has A and B players. And every manager needs to decide how to spend his or her time training - does she work hard with the B player trying to bring them up to speed? Or analyze an A player's performance to see how they can get even better? The answer? Follow the numbers.