NEW DELHI, March 8: The annual rate of inflation dropped to 5.19 per cent for the week ended February 21, the lowest in 1998, due to easing in prices of primary food articles.The annual inflation, based on Wholesale Price Index (WPI), fell by 0.26 percentage points during the week to 5.19 per cent (provisional) compared to 5.45 per cent (P) the week before and 7.85 per cent in the corresponding week of last year.The WPI for "all commodities" (base: 1981-82=100) for the week was at 338.3 (P) As against 338.8 (P) The week before, showing a decrease of 0.1 per cent.Meanwhile, the year 1997 ended with an inflation of 5 per cent as rate of increase in prices.