A number of design flaws have limited the effectiveness of the scheme. In the initial 2005-07 period, emission caps were not tight enough to drive a significant reduction in emissions. The total allocation of allowances turned out to exceed actual emissions. This drove the carbon price down to zero in 2007. This oversupply was caused because the allocation of allowances by the EU was based on emissions data from the European Environmental Agency in Copenhagen, which uses a horizontal activity-based emissions definition similar to the United Nations, the EU ETS Transaction log in Brussels, but a vertical installation-based emissions measurement system. This caused an oversupply of 200 million tonnes (10% of market) in the EU ETS in the first phase and collapsing prices.