The pressure on the big four supermarkets intensified during the 12 weeks ended on March 2nd, according to the latest data available from Kantar Worldpanel. That came as Aldi's year-on-year growth rate accelerated to a record 33.5% pace so that it now accounts for 4.3% of the market. Lidl's share also hit a historical high, at 3.2%. Adding to their woes, the overall rate of growth in the grocery market, of 2.2%, fell further from the last period, which was the lowest since mid-2005, mainly as a result of falling inflation. Sainsbury was the exception amongst the big four, which also includes Asda, Morrison and Tesco, managing to hold on to its 17% of the market. Waitrose also shrugged off the pressure from the discounters, obtaining its highest ever market share of 5%.Thus, Asda, Morrison and Tesco all saw their markets shares decline, with the latter two seeing a decline in actual sales. The Co-operative saw sales grow 0.7% and only a marginal drop in share to 6.1%.Over the past three years Waitrose, Aldi and Lidl combined have taken 3.5 percentage points (£4.4bn per year) from their competition, placing further pressure on their competition to lower their prices to fend them off. AB