extensive: almost every place in the country is connected by bus, from largest cities to the villages; in addition there are international routes (mainly to countries of Western Europe with small Serb diaspora). Routes, both domestic and international, are served by more than 100 bus companies, biggest of which are Lasta and Niš-Ekspres. , there were 1,959,584 registered passenger cars or 1 passenger car per 3.5 inhabitants. Serbia has 3,819 kilometers of rail tracks, of which 1,279 are electrified and 283 kilometers are double-track railroad. The major rail hub is Belgrade (and to a lesser degree Niš), while the most important railroads include: Belgrade–Bar (Montenegro), Belgrade–Šid–Zagreb (Croatia)/Belgrade–Niš–Sofia (Bulgaria) (part of Pan-European Corridor X), Belgrade–Subotica–Budapest (Hungary) and Niš–Thessaloniki (Greece). Although still a major mode of freight transportation, railroads face increasing problems with the maintenance of the infrastructure and lowering speeds. The rail services are operated by Srbija Voz (passenger transport) and Srbija Kargo (freight transport). There are three airports with regular passenger traffic. Belgrade Nikola Tesla Airport served 5.6 million passengers in 2018 and is a hub of flagship carrier Air Serbia which carried some 2.5 million passengers in 2018. Niš Constantine the Great Airport is mainly catering low-cost airlines. Morava Airport is currently only served by Air Serbia. Serbia has a developed inland water transport since there are 1,716 kilometers of navigable inland waterways (1,043 km of navigable rivers and 673 km of navigable canals), which are almost all located in northern third of the country. The most important inland waterway is the Danube (part of Pan-European Corridor VII). Other navigable rivers include Sava, Tisza, Begej and Timiş River, all of which connect Serbia with Northern and Western Europe through the Rhine–Main–Danube Canal and North Sea route, to Central Europe via the Tisza, Begej and Danube Black Sea routes, and to Southern Europe via the Sava river. More than 2 million tons of cargo were transported on Serbian rivers and canals in 2016 while the largest river ports are: Novi Sad, Belgrade, Pančevo, Smederevo, Prahovo and Šabac. Economic indicators The following table shows the main economic indicators Labour In 2021, the labour force was estimated at 3.201 million and employment stood at 2.848 million persons (formal employment amounted to 2.473 million while informal was at 0.375 million). Employment rate (among population aged 15 and over) is comparatively low and stood at 48.6%; of those employed; of those employed 15.9 worked