Imagine you're the CEO of a hypothetical mutual fund company with 10 different mutual funds and 40 managers of those funds. Now, imagine you didn't know which manager had bought which stocks. Absurd, right? You would never be able to make adjustments as far as which managers were good stock pickers and which ones were not.
As absurd as this scenario is, there's an equivalent situation in most organizations in that managers are not held accountable for which employees they decide to "invest" in by hiring them. It's very rare that organizations hold hiring managers accountable for their hiring decisions, although the decision to hire an employee is really very similar to the decision to buy a stock- in either case, you are taking a calculated risk and making a prediction about future performance based on past performance.
A very simple way to remedy this is to come up with criteria, such as the ones listed below. For each one, you can create a five point scale, with 1 meaning the candidate would not likely be successful on that criterion, and a 5 meaning that the candidate, in your view, is highly likely to be successful in this area.