Ultimately, because of the comfort level with the concepts involved in theory‐driven risk modeling, most quants tend to use theory‐driven risk models rather than empirical risk models. It is worth noting that these two kinds of risk models are not mutually exclusive. Quants may perfectly reasonably use a combination of both, if they deem it appropriate. A small minority of managers also attempt to use their judgment and discretion to monitor market behavior and, should it become clear to them—for example, from the way that the financial media and their peers in the business are behaving—that there is a “new” risk factor that is driving markets, they build a made‐to‐order risk factor to measure this temporary phenomenon. When they see that the new driver has faded in importance, they can remove it from the risk model, again using their judgment.