Reasons for the Changes to Global Electricity Generation between 1973 and 2006
The most significant increase was nuclear; this could be due to growing public acceptance, as memories of Chernobyl 1986 fade, and the increasing desire of governments to produce energy within their own country, to minimise the risk of reduced supply due to political conflicts, and of other nations being able to exert soft power backed up by reliance on their natural resources. Unlike solar, wind, and fossil fuels, nuclear power requires very little from the country's landscape and environmental circumstances, and necessary materials can be imported from politically stable regions, e.g. uranium from Canada. France now produces most of its electricity from nuclear power, and has therefore increased its energy security, by decreasing its reliance on Russian natural gas.
The most significant reduction is that of oil, from 25% to 6%. This is largely due to reserves becoming depleted; many countries, including the UK, have already passed peak oil, and so have been forced to diversify their energy sources. This has therefore contributed to the increased use of natural gas, which remains abundant in the USA and Russia.
The slight increase in the use of coal is likely to be at least partially due to the rise of China, which has used its abundance of domestic coal reserves to drive rapid economic growth.
Whilst the percentage of electricity production from biomass and geothermal has grown only slightly, in absolute terms, the growth has been very significant, as, globally, three times more electricity is used now than in 1970. As with the growth in nuclear, solar, and wind, this is partly due to improved technology. Renewables are gaining momentum as concerns about climate change increase, and developing countries are starting to rely on biomass, as it is cheap, and fits well with the large land area and agricultural industry dominance of countries such as Brazil.