what are places like the Cayman Islands, Luxembourg, or Ireland doing on the list?
Two simple facts help to explain these anomalies.
Firstly, despite having a population of just 60,000 people, the Cayman Islands is a hedge fund capital with over 10,000 funds domiciled there. Luxembourg makes the list for similar reasons, given that it is the European-based tax shelter equivalent.
Ireland, on the other hand, is the overseas headquarters for many U.S.-based tech giants like Facebook or Alphabet. Apparently, these corporations like to hold their overseas profits in highly-liquid Treasurys, rather than paying a repatriation tax to bring the cash back to American soil.