Meanwhile, Andreas Papandreou founded the Panhellenic Socialist Movement (PASOK) in response to Karamanlis's conservative New Democracy party, with the two political formations alternating in government ever since. Greece rejoined NATO in 1980. Greece became the tenth member of the European Communities (subsequently subsumed by the European Union) on 1 January 1981, ushering in a period of sustained growth. Widespread investments in industrial enterprises and heavy infrastructure, as well as funds from the European Union and growing revenues from tourism, shipping and a fast-growing service sector raised the country's standard of living to unprecedented levels. Traditionally strained relations with neighbouring Turkey improved when successive earthquakes hit both nations in 1999, leading to the lifting of the Greek veto against Turkey's bid for EU membership.

Answer this question, if possible (if impossible, reply "unanswerable"): In what year did Greece rejoin NATO?
1980