Sales over the Thanksgiving weekend dropped for the first time since 2009 despite longer opening hours and a record number of sales, according to the retail industry's main trade group.

Aggressive discounting and a controversial decision by many retailers to open earlier on the Thanksgiving day holiday appear to have failed to entice shoppers, as estimated total spending over the weekend fell to $57.4bn, down 2.7% from a year ago, according to the National Retail Federation (NRF). The NRF still expects total holiday sales through year-end to rise by 3.9% from a year ago.

The gloomy sales figures, released Sunday, come in a week packed with key economic data about the health of the US economy. On Monday, the Institute for Supply Management (ISM) said US manufacturing gained momentum in November, with its monthly poll rising to 57.3 from 56.4. Any index reading above 50 indicates expanding activity. November’s figure was the highest since April 2011.

Data on housing and auto sales is due this week. But the key economic data comes on Thursday with the latest update on US gross domestic product (GDP) and Friday, when November’s nonfarm payroll jobs report is released.

Friday’s job report is seen as particularly crucial. It will be the last before the Federal Reserve meets to discuss whether or not to cut back – or “taper” – the $85bn a month it is pumping into the financial markets through its quantitative easing (QE) stimulus programme. Incoming Fed chair Janet Yellen and incumbent Ben Bernanke have tied any cuts in QE to the unemployment rate.

Paul Dales, US economist at Capital Economics, said the Thanksgiving sales figures were headline-grabbing but statistically irrelevant. “You can’t pay too much attention to what happens over one or two days, what matters is the next two or three months,” he said.

Economically, Dales said the Thanksgiving weekend sales dip came amid falling unemployment and a rising housing market and may have had more to do with the structure of the sales than a statistically significant shift in consumer spending.

This year, many retailers started sales earlier and were discounting well ahead of the traditional Black Friday sales. Opening on Thanksgiving day appears to have pulled sales away from Black Friday. Some 45 million people went shopping on Thanksgiving day, according to the NRF, a rise of 27% from last year. But the numbers of people shopping on Friday increased by just 3.5% to 92 million.

Online sales too may have held store sales. Total e-commerce sales topped $20.6bn in the first 29 days of this holiday season, ComScore said on Sunday. That figure represents a 3.1% rise over the period between 1 November and Black Friday last year.

Even as the NRF’s figures came in, another survey painted a little less gloomy picture of holiday shopping. Sales at brick-and-mortar stores posted an estimated 2.3% gain to $12.3bn, according to a report from ShopperTrak, a Chicago-based research company. ShopperTrak predicts that holiday purchases will grow by 2.4% this year, a rise but still the weakest since 2009.

Ken Goldstein, economist at the Conference Board in New York, said the figures were yet more evidence that the economy was “muddling through”. “The figures are not good but not terrible. Growth stalled in the Spring and we are now back to where we were then,” he said.

Rather than the weekend’s lackluster sales, Dales said his focus was on Friday’s nonfarm payrolls. Last month the Labor Department announced it had added 204,000 new jobs in October, higher than expected. Figures for August and September were also revised upward. Economists are predicting that the US added around 185,000 new jobs in November. Goldstein predicts the figure will be lower, at around 150,000-160,000, but anything over 175,000 is likely to add pressure on the Fed to cut QE, said Dales.

Gus Faucher, senior economist at PNC, said it was too early to tell much from the start of the Christmas shopping season. “They tell a piece but not the whole story,” he said. “But in the next few days we should get a clearer picture of what is going on,” he said.