The economy of Odessa is based on its port and its close distance to nearby ice-free ports in the mouths of the Dnieper, the Southern Bug, the Dniester and the Danube rivers. During the Soviet period, it was the USSR's largest trading port. Since Ukraine's independence, Odessa remains the busiest international port in the country. Odessa is also a home to almost 5% of all IT companies registered in Ukraine. It helps the city to thrive and attract talented software programmers from other cities of Ukraine and abroad. 