Unilateral anti-avoidance rules are very complex but not very effective.
What can be observed in practice is a proliferation spiral. States must
continually amend their unilateral rules to react to new tax planning
schemes.12 In 1996, recognizing this lack of effectiveness, the G-7 Finance
Ministers mandated the OECD to launch a project to counteract ‘harmful
tax competition’ (OECD, 1998). The original purpose was to persuade tax
havens to abolish harmful tax practices. In particular, they were encouraged
to change their national tax laws so that it was no longer possible
for a tax avoider to merely ‘book’ some economic activity in the respective
haven without any underlying ‘real’ economic activity. In addition to
that the project also aimed at so-called preferential tax regimes in high-tax
countries, i.e. rules which tried to attract foreign capital by offering better
treatment than was available to domestic investors.