It is not easy to establish a causality link, but in some cases this has been quite evident, because even the targeted leaders or the advisers, the circle around them, have confirmed that the impact of sanctions or the prospect of the continuation of sanctions has affected their calculations.
Sometimes it is possible to ascertain that there is a relationship of causality simply by taking a look at the chronology. In some cases, it is pretty evident, but in many cases, what you usually have is a combination of factors leading to these decisions.
Sanctions can be effective and not simply by having a direct impact on the calculations of the responsible leaders. Sometimes the sanctions can create conditions that foster a climate, or they bring about, for example, defections among the members of the inner circle of the leaders, which helps bring about this kind of behaviour.
As I mentioned in my presentation very briefly, sanctions are not only, or primarily, or exclusively about influence, but about changing the behaviour of the targeted leaders. They fulfill a number of functions in international relations, and sometimes the sanctions are actually designed to just create an incentive for the leaders to negotiate, to participate in a process of negotiation that is influenced by many other factors.
In many cases, as long as the sanctions have actually provided an incentive for parties participating in a conflict to actually negotiate, then we can consider the sanctions to have been successful, even if they have not brought about a complete change in the behaviour of the leaders, or even if they have not managed to interrupt completely the prescribed behaviour.