The Commerce Department said Wednesday that seasonally adjusted retail sales dropped 0.3 per cent from the previous month. Sales have risen 4.3 per cent in the past 12 months, slightly below their historical pace.
Auto sales fell 0.8 per cent in September, after revving up 10.4 per cent in August.
Dealers sold cars and trucks at an annual pace of 16.43 million vehicles last month, down from a rate of 17.5 million in August, according to automakers. While auto sales have helped drive economic growth for much of the year, the recent slip was enough to dent overall retail sales in September.
Falling gasoline prices also contributed to a decline in retail sales, as purchases at service stations were off 0.8 per cent in September. Drivers are spending much less at the pump, as average U.S. prices have dropped to $3.19 a gallon from $3.40 a month ago, according to the AAA. That should eventually free up income for consumers to spend elsewhere.
Purchases of clothing dropped 1.2 per cent last month and spending on building materials fell 1.1 per cent.
"It's hard to square the drop in underlying sales with the strengthening labour market and the boost to real incomes from lower gasoline prices," said Paul Diggle, an economist at Capital Economics. "As such, we expect sales growth to strengthen again before too long."
On the other side of the ledger, spending at electronics stores rose 3.4 per cent last month. Electronics sales probably improved in September thanks in part to the release of new iPhones by Apple. Apple says it sold more than 10 million iPhone 6 and 6 Plus models, a record for a new model, in the three days after the phones went on sale.
"Given the record number of iPhone pre-orders in the month, it is a pretty safe bet that those devices were responsible for most of the gain," said Jennifer Lee, a senior economist at BMO Capital Markets.
Excluding autos, retail sales still dipped 0.2 per cent last month.
Increased consumer spending could help buffer the U.S. economy from the consequences of a broader global slowdown. Roughly 70 per cent of all U.S. economic activity is driven by consumer spending.
The German government on Tuesday downgraded its economic growth projections, while much of Europe copes with high unemployment and diminished prospects. China's propulsive growth has started to fade, and consumers in Japan are still spending cautiously after a big sales tax increase. Last week, the International Monetary Fund trimmed its global growth forecasts for this year and next, citing weakness in Japan, Latin America and Europe.
In the U.S., future gains in retail spending will likely hinge on job growth.
Employers added 248,000 jobs last month, according to the Labor Department. Job growth has averaged 227,000 a month through the first nine months of 2014.
Each new job increases the number of paychecks in the economy. Still, wage gains have been sluggish since the recession ended in 2009, and that's led many people to be more cautious about spending money. Average hourly pay fell a penny to $24.53 in September. That's an increase of less than 2 per cent over the past year, meaning pay is barely matching inflation.