When we say we have pegged something, we mean we have identified and established it. In other words, we have determined or pinpointed it. There are several synonyms we can use to express this phrase, such as "narrowed down", "concluded", "assigned", "confirmed", "diagnosed", "figured out", or "marked". Each of these synonyms carries a slightly different meaning depending on the context in which it is used. However, they all share the common idea of having established a particular fact or piece of information. So, whenever we want to describe that we have successfully identified or established something, we can use any of these synonyms to replace "have pegged".