In the UK, there is no single moment when someone moves from childhood to adulthood; instead responsibilities and permitted activities build up over time. For example, a person must be 17 before they can leave home without parents' consent or hold a license to drive and 18 before they can sit on a jury or buy alcohol. I think this illustrates that, so far, we have viewed attainting adulthood as a process rather than a single event.
Most democracies consider 18 the right age to enfranchise young people. So far in the EU, only Austria and Scotland have lowered the voting age to 16 for national elections.
A 2009 report by the Youth Citizenship Commission stated that the voting age is not the principal factor in encouraging young people's interest and involvement in politics and citizenship.