That is a question that is actually the object of some dissertations in the academic world, because the definition of “effectiveness” is not a single one. There are various levels of objectives when a country imposes autonomous sanctions.
Of course, the ultimate and final objective is to effect a change in the behaviour of the offending party. It is not the only objective. There are many interim objectives that could be obtained—for example, constricting the ability to act financially and economically. However, it is also an important signal our government can send: These actions of malicious individuals or entities are unacceptable in a global context. There are, of course, other ways to signal this. This is a pretty powerful and clear one. There is a bit of a shaming factor that comes with it, as well. It also helps by sending a dissuading element to other potential malicious actors. Finally, I would say it serves as a bit of an inspiration for other countries with autonomous sanctions legislation to follow us and join in our actions. There is a multiplicity of potential effects that we would need to assess at any given time.
Let's take the case of Russia, for example. Have sanctions been effective? Depending on which of these definitions you observe, I would say yes. Russia's ability to wage its war has been significantly reduced. Russia's economy has shrunk. Over 1,000 international companies have left Russia. Through very strict export controls on dual-use technology, Russia's ability to integrate computer chips and highly sophisticated material into its weapons supply chain has been significantly reduced, limiting, over the long term, its capacity to wage the kind of brutal war it is waging in Ukraine.