tax resident by that same amount, on the principles of avoiding double taxation of the same activity. Research in 2013–14 showed OFCs harboured 8–10% of global wealth in tax-neutral structures, and acted as hubs for U.S. multinationals in particular, to avoid corporate taxes via base erosion and profit shifting ("BEPS") tools (e.g. the double Irish). A study in 2017 split the understanding of an OFC into 24 Sink OFCs, to which a disproportionate amount of value disappears from the economic system), and five Conduit OFCs, through which a disproportionate amount of value moves toward the Sink OFCs). In June 2018, research showed that major onshore IFCs, not offshore IFCs, had become the dominant locations for corporate tax avoidance BEPS schemes, costing US$200 billion in lost annual tax revenues. A June 2018 joint-IMF study showed much of the FDI from OFCs, into higher-tax countries, originated from higher-tax countries (e.g. the UK is the second largest investor in itself, via OFCs). Definitions Core definition The definition of an offshore financial centre dates back to academic papers by Dufry & McGiddy (1978), and McCarthy (1979) regarding locations that are: Cities, areas or countries which have made a conscious effort to attract offshore banking business, i.e., non-resident foreign currency denominated business, by allowing relatively free entry and by adopting a flexible attitude where taxes, levies and regulation are concerned.” An April 2007 review of the historical definition of an OFC by the IMF, summarised the 1978–2000 academic work regarding the attributes that define an OFC, into the following four main attributes, which still remain relevant: In April 2000, the term rose to prominence when the Financial Stability Forum ("FSF"), concerned about OFCs on global financial stability, produced a report listing 42 OFCs. The FSF used a qualitative approach to defining OFCs, noting that: Offshore financial centres (OFCs) are not easily defined, but they can be characterised as jurisdictions that attract a high level of non-resident activity [...] and volumes of non-resident business substantially exceeds the volume of domestic business. In June 2000, the IMF accepted the FSF's recommendation to investigate the impact of OFCs on global financial stability. On the 23 June 2000, the IMF published a working paper on OFCs which expanded the FSF list to 46 OFCs, but split into three Groups based on the level of co-operation and adherence to international standards by the OFC. The IMF paper categorised OFCs as