The EU ETS covers operators from power production, industrial processes and aviation limited to flights within the European Economic Area. The covered GHG gases are CO₂ and N₂O and PFC emissions from certain industries. EU-wide, some 11,000 installations are included in the EU ETS. There are around 600 installations in Finland. Greenhouse gas emissions in the emission trading sector and non-emissions trading sector from 2005 to 2020 are presented in Table 4.1. At the beginning of 2020, the EU ETS was linked with Switzerland's trading system, allowing more flexibility for the use of allowances for both entities. EU Emissions Trading System The EU ETS continues to be the most important economic policy instrument for reducing emissions in the EU and its Member States. Under the system, emissions are limited under an EU-wide cap, which sets the maximum amount of emissions for all operators obliged to participate in the system. The system is divided into periods for which the emissions reduction target and the representative cap are established. In addition, more significant rule changes usually take place as the period changes.