In 1975 the voting system of 12, 10, 8 etc to 1 point was introduced. It had always been the rule that all participating countries and only the participating countries could vote each year.

In 2004 this rule changed, because due to the amount of countries wishing to participate, a semi final round had to be introduced.
Pre-qualified for the final were the top ten placed countries plus the 'Big Five' Germany, France, United Kingdom, Spain and Italy (which however is currently inactive).
The Big Five are always qualified for the final and will never have to take part in the semi finals.

These 14 countries would not participate in the semi final, but they were all allowed to vote in it.

All other countries would go through the semi final round.

One further rule is that only countries broadcasting the semi finals are allowed to vote in it.
Countries not participating and not broadcasting the semifinal are not allowed to vote.