Year-on-year the numbers still look good with sales growing at 35% in the 12 months to 5 September. However, the discounter only managed 3.3% growth for the four weeks to 5 September year-on-year.
The period ironically coincides with the time Armin Burger took over from Paul Foley as MD.
Aldi and the other discounters have suffered "the end of the age of rapid discounter growth", according to Mike Watkins, Nielsen's senior manager of retail services. Nielsen figures shown to The Grocer reveal the big four have all but closed the gap on Aldi, Lidl and Netto in terms of growth. In December, the discounters were showing sales growth of 31% compared with 5.8% at the big four. But discounters' growth has slowed to 8.5% in September compared with 4.7% at the big four.
"The main reason the discounters' growth has slowed is that it's very hard to continue showing sales increases on such huge growth," said Watkins. "The discounters will need to raise their game if they are to maintain the loyalty of increasingly fickle UK customers."
The supermarkets had done an "excellent job" of highlighting their value credentials, he added. Tesco had launched its discounter ranges, Sainsbury's launched its Switch and Save campaign to drive people to its own label rather than brands and Waitrose had launched the Essential Waitrose range.
However, Nielsen's research indicates 43% of consumers have visited a discounter in the past 12 weeks compared with 40% at this time last year.
The rise in shopper numbers was partly down to an increase in store numbers, said Watkins, but it proved consumers were not abandoning discounters. "As a retail format, they are better understood by the public than a year ago."
Accounts filed this week confirm the phenomenal growth of Aldi in 2008 its turnover and pre-tax profits both rose 32%, to £2bn and £92.7m respectively, in the year to December 2008.