The US economy shrank 5.5 per cent in the first quarter of 2008, according to a final revised estimate of the US Commerce Department today, dpa reported. The final figure was improved slightly from a previous estimate of a 5.7-per-cent contraction. The massive drop comes as the United States battles its longest recession since the Great Depression. The world's largest economy shrank 6.3 per cent in the fourth quarter of 2008.