Which year was the first year a semi-final was introduced in the Eurovision Song Contest?

Explanation

Eurovision Song Contest 2004 took place in Istanbul, Turkey. It was the firrt time the competition included a semi-final round to enable more countries to participate. 36 countries had entered the competition, but only 24 could fit in the final. The Big Four (France, Great Britain, Spain and Germany) qualified directly for the final. The same was true for the best 10 countries from 2003 and the 10 best performances in the semi-final. Ukraine won.