The total volume of greenhouse gas emission generated by the activities of an economic unit over a given period of time, usually 12 months, measured in tonnes of carbon dioxide equivalent (CO₂e). The official estimate of the UK carbon footprint produced by the UK government includes emissions generated in the domestic production of goods and services for domestic consumption, in the worldwide production of goods imported into the UK, and in the daily activities of UK households. In 2012 imports contributed 45 per cent of the UK carbon footprint, whereas the shares of domestic production and direct emissions by households were 38 and 17 per cent, respectively.