Bulgaria’s capital city, Sofia, is the political and economic centre of the country. With about 1.2 million inhabitants, or around 16.5% of Bulgaria’s population, Sofia contributed approximately 33% of the country’s GDP in 2007. The population has risen noticeably since 2001, in contrast to the national demographic trend, as the city has flourished during the transition period, attracting more than 60% of Bulgaria’s total foreign direct investment. Sofia’s economic growth has also led to overcrowding on public transport and traffic congestion on the city’s main roads. Sofia ranks 29th in the European Green City Index, with a score of 36.85 out of 100. As in the cities of other post-communist countries, years of neglect and underinvestment have had a detrimental impact on Sofia’s environment. The city is also located towards the bottom of the income scale in the index, a factor that appears to be correlated significantly with environmental conditions.