Import activity for the US back-to-school season is down this year for the months of June and July, suggesting either a change in buyer behaviour or a slowing of demand.

The US back-to-school shopping season traditionally starts in the two months before school terms restart in early September. In previous years this has led to a spike in imports of kids apparel and education-related equipment in June and July.

Over the past six years June imports were 18% higher than the average, July has been up 27.1% and August by 18.6%, data from trade intelligence platform Panjiva shows.

This year, however, 2017 imports in June were unchanged, and therefore down by 24.7% on a year earlier. Panjiva suggests this could be down to the Petya cyber attack delaying shipping record submissions through APM Terminals' ports.

It offers three other explanations. Imports may have been hit by a change in buyer behaviour – namely retailers leaving purchasing later or shortening inventory holding cycles. Data for July should answer that question.

A second possible explanation is a slowing demand. "The recent decline in consumer confidence may be evidence of this."

A final driver, Panjiva says, may be a reallocation in spending to other products. Imports of laptop computers were 16% higher in May and 5% higher in June, data shows.

Meanwhile, a survey by Deloitte forecasts that this year's total back-to-school spending is expected to reach US$27bn, with mass merchants and off-price retailers becoming the go-to venues, while traditional department stores and speciality clothing retailers take a back seat.