Researchers have developed a new framework to assess a country's self-sufficiency in electricity as a measure of electricity supply security. Of the countries studied, results indicate that Greece and the UK became much more dependent on imported electricity and fuel between 2000 and 2005. Poland has become electricity independent, but relies heavily on coal. Germany reduced its use of coal in electricity generation from 51.1 per cent in 2000 to 43.6 per cent in 2005; this was a consequence of a clean fuel policy which has seen the share of domestic wind power, biomass and waste increase. Germany reduced the share of electricity produced using nuclear fuel from 29.7 per cent to 26.3 per cent, reflecting a policy to phase out nuclear power. Despite increases in renewable energy, this was not enough to offset reliance on imported oil, coal and gas and Germany's electricity dependence increased slightly from 48.6 per cent to 48.9 per cent. Greece also reduced its reliance on domestic coal from 63.9 per cent to 59.4 per cent. The contribution of electricity generated from hydropower increased from 7.7 per cent in 2000 to 9.4 per cent in 2005. Use of natural gas also increased thanks to a policy which requires new fossil fuel power stations to be gas fired. However, natural gas is entirely imported from Russia and Algeria. Overall, Greece was an importer of electricity and its dependency on imports increased from 27.5 per cent in 2000 to 33.2 per cent in 2005. In the UK the share of coal in the fuel mix for electricity generation increased by 2.3 per cent between 2000 and 2005. At the same time, the UK has become more reliant on imported fossil fuel as its own resources have depleted. The share of domestic wind power and biomass increased, but this did not offset dependence on imported coal and gas. Therefore electricity dependency rose sharply from 40.7 per cent to 51.4 per cent. Poland was the only country to become import independent in the electricity sector. Poland's electricity dependency on imports dropped from 0.4 per cent in 2000 to 0 per cent in 2005. It kept control over its electricity generation resources and improved its ability to export electricity. Coal is the dominant fuel and is mainly sourced from within Poland. Other fuels play a very small role. Wind energy reached a 0.1 per cent share in 2005 and biomass increased from 0.2 per cent to 1.3 per cent. The researchers note that feed-in-tariffs to support renewable energy have produced different results in Greece and Germany. Similarly, the UK and Poland have both used renewable obligation schemes but, especially in Poland, the share of renewable energy indicates the policy has been unsuccessful.