The European Emissions Trading Scheme (ETS) is a debated way to reduce emissions. The researchers used a model called DART to study different allocation plans for carbon allowances. They found that trading these allowances between countries in the EU could vary, affecting prices and competitiveness. Until all countries decide on their allowance plans, the total number of available allowances remains uncertain. The research highlights how these decisions can impact trade flows, prices, and the roles of newer EU countries in the ETS.