Supermarket giant Tesco is still at the top of the supermarket charts this week, and it retains its leading position in Retail Weeks Top 500 Survey. The survey, compiled by Emap's Retail Knowledge Bank , showed that sales growth among the country's top 500 retailers grew by 5.9% between 1999 and 2000. Smaller operators saw their market share squeezed by 7.5% because of the competition from the supermarket giants. The picture for these retailers is however, not ideal.