15. The ratio of energy consumption to economic
output is expressed as the energy intensity of an economy
and is a common proxy for a national energy efficiency rating.
The UK's energy intensity since 1973 is shown overleaf in Table
1and demonstrates the de-coupling of economic growth, as defined
by GDP, from energy consumption.
The following table reveals the same story applying
to the development of a number of economies as well as for the
process of economic development overall.
Table 2: Energy intensity of industrialised
countries since 1850
Source: Factor four: doubling wealth - halving
resource use, Weizacker & Lovins, London, 1997, Earthscan
16. Changes to energy intensity are the result of
both changes in efficiency of supply and use as well as changes
in the structure of the economy (for example, a decline of activities
with high energy-use such as manufacturing and growth of the high-value,
low energy consuming service sector). DTI and International Energy
Agency (IEA) estimates show that structural change, for example
the 'export of energy intensive manufacturing', contributed about
10 per cent to the UK's fall in energy intensity since 1973 with
the bulk of improvement due to efficiency gains in industry.
17. Energy intensity by itself does not reveal
the balance of environmental impacts of different fuels. For example
it is the carbon intensity of energy supply is the key
indicator for the contribution to global warming.