that whilst aviation is an important industry in its own right, the most important contribution is as "… a facilitator of growth for the economy as a whole." Environmental groups dispute the economic benefits that are claimed for air transport, and the OEF reports have been specifically challenged. The Aviation Environment Federation (AEF), publishing the Rebuttal of Oxford Economic Forecasting Report, has labelled the 2006 OEF report "biased and misleading". AirportWatch, an umbrella movement for national environmental organisations and airport community groups opposed to aviation expansion, has produced a critique of the 2006 OEF report and the DfT's reliance on economic research that has been "… sponsored by the aviation industry." In response to government policy supporting further growth in aviation, Friends of the Earth (FoE) published Pie in the Sky in September 2006. This study concludes that the economic benefits of aviation have been exaggerated, and that the costs arising from environmental damage, as well as to other sectors of the economy, are ignored. Also published in 2006, the Environmental Change Institute study Predict and decide – Aviation, climate change and UK policy re-examined the economic arguments made in favour of aviation, concluding that restricting future growth would not necessarily be detrimental to the economy, and could potentially result in some economic benefits. Direct economic contribution In terms of direct contribution to the UK economy, air transport is an £11.4 billion industry, a figure which represents 1.1 per cent of the country's economy. It employs 186,000 people (full-time equivalents), and indirectly supports an additional 334,000 jobs, although the inclusion of indirect employment as an economic benefit of air transport is disputed. In terms of productivity the aviation industry in 2004 was the third most productive, after the oil/gas extraction and utilities sectors, exceeding the national average by a factor of two and a half. The industry is also very capital intensive, accounting for up to 3.5 per cent of total UK business investment in the period 2000 to 2004. Air transport was directly responsible for £3.6 billion in tax and national insurance contributions in 2004/5, which includes £0.9 billion raised in Air Passenger Duty (APD), a figure set to double after APD rates were doubled in February 2007. Because of the global nature of the industry, article 15 of the Chicago Convention effectively prevents the imposition of fuel duty on aviation, and the industry does not pay Value Added