Let me make one comment, and then I'll ask my colleague to add to it.
We are not naive about the role that sanctions might play. It is but a single tool in a tool box that we have to use. Sanctions are less impactful, perhaps, in a place like North Korea because their external trade is so minimal. In fact, I think something like only 10% of their economy is trade-dependent. It is a very self-sufficient economy. They can produce a lot of things domestically. What we're trying to do is ensure that they can't procure internationally the kinds of materials and technologies that are relevant to their weapons programs. There we still have work to do. The fact is that some countries are not implementing the sanctions as fully as they could, and we're working with those countries to plug those gaps.
Perhaps Sarah has something further to add.