The researchers calculated that a population which followed a Nash strategy would contract 100 times more infections than one which followed a utilitarian strategy.

ECONOMIST: Flu vaccination

Westminster, home to Victoria coach station, a gateway for eastern Europeans seeking employment in the UK, has long been campaigning for a change in the way London's population is calculated.

BBC: Councils call for migrants fund

For these reasons some argue that youth unemployment is better and more accurately represented by using a ratio, calculated as the share of unemployed, as a percentage of the whole youth population.

BBC: Global youth unemployment: Making sense of the numbers

Three years ago, the Swiss Statistical Office calculated that, with declining birth rates, stabilising the level of immigration would cut the working population by almost one-third by 2050.

ECONOMIST: Switzerland: Foreign relief | The