It's a good question.
The large IT firms make up one of the top two sectors in terms of aggressive tax avoidance. I'll give you one example. Microsoft is facing the largest tax bill in global history. The U.S. Internal Revenue Service, IRS, is pursuing Microsoft for close to $30 billion and that may be just the tip of the iceberg, because the case they're pursuing in the courts is for a limited period of time but would cover a larger period.
The other sector that is very highly tax aggressive is big pharma. It's incredibly easy for both IT and pharma to shift their intellectual property into countries or into structures where it's easy to avoid tax because of royalty payments on intellectual property going into structures that provide tax shelters.
Even countries that are not necessarily full-fledged tax havens have created structures that allow discounted tax rates; these are called patent box regimes.
The six largest U.S. pharma companies have actually paid negative tax in the United States over the last two years and it's very clear that the vast majority of their income and profits are generated in the United States, but they're reporting that income in offshore jurisdictions and actually have received refunds collectively over the last two years.