national tax, and so the DST would reduce net Irish tax (e.g. Google Ireland would offset its DST against Irish CT). In April 2018, the EU Commission's GDPR rules forced Facebook to move 1.5 billion of the 1.9 billion Facebook accounts hosted in Ireland ( 79% of the 2.4 billion total global Facebook accounts), back to the U.S. The April 2018 Irish High Court ruling in the Max Schrems EU data-protection case could make Ireland even less attractive to Facebook. The EU Commission's long-standing desire to introduce a Common Consolidated Corporate Tax Base ("CCCTB"), would have a more severe effect on Ireland's CT system. US countermeasures (2016–2018) The U.S. has had a contradictory approach to Ireland's CT system. U.S. investigations, from the first U.S. IRS study in 1981, up to and including 2013 U.S. McCain–Levin Senate investigations into Apple's tax structures, label Ireland as a "tax haven" for U.S. multinationals. However, it was the EU and not the U.S., that forced Ireland to close its Double Irish BEPS tool in 2015. While the Obama administration supported the McCain–Levin findings on Apple, it came to Apple's defense in 2016 when the EU Commission fined Apple €13 billion for taxes avoided over 2004–2014. This contradiction is chronicled in "political compromises". The source of the contradiction is ascribed to the findings of U.S. tax academic, James R. Hines Jr.; Hines is the most cited author on tax haven research, and his important 1994 Hines–Rice paper was one of the first to use the term "profit shifting". The 1994 Hines–Rice paper showed that low foreign tax rates [from tax havens] ultimately enhance U.S. tax collections. Hines' insight that the U.S. is the largest beneficiary from tax havens was confirmed by others, and dictated U.S. policy towards tax havens, including the 1996 "check-the-box" rules, and U.S. hostility to OECD attempts in curbing Ireland's BEPS tools. However, by 2014 Ireland had become the leading destination for U.S. corporate tax inversions, and in 2016, the Obama administration decided to move against Ireland's CT system by amending the U.S. tax-code to block the proposed $160 billion Pfizer–Allergan Irish corporate tax inversion, which would have been the largest tax inversion in history. The most serious threat to Ireland's CT system, and Ireland's economic model came in December 2017 with the passing of the Tax Cuts and Jobs Act (TCJA) by the Trump administration. Parts of the TCJA are specifically