Adopt this policy if you need to grow and develop your cities in a hurry. However, it will prevent you from expanding by any means short of military conquest.
When commerce is viewed as a zero-sum game which favors parties outside the nation, and this is coupled with a negative economic turn, then economic isolation becomes particularly appealing as a political solution. The Tokugawa Shogunate’s closing of Japan is one of history’s most famous examples of isolationism, lasting for about 250 years. But the absence of foreign trade can result in stagnation and a lack of growth, and ultimately shock as the economy re-integrates into the world.