Unless the money is sitting in a money bin like Scrooge McDuck's, it's not just "sitting". Banks are allowed to lend out money based some multiple of current deposits. They can also invest that money in other ways (i.e. stock market), in order to generate enough profit to pay the interest on the deposits. So the money is circulating anyway. Of course, with offshore deposits it's not circulating locally, so you're losing out on the local stimulation, and on local taxes.