Retail sales volume fell 5.3 per cent in December, marking a tenth successive month of decline in the biggest month of the year for many stores.

For the first time, the Retail Sales Index from the Department of Statistics detailed the value of imports by households, giving insight into the impact of online shopping from overseas sources.

In total, shoppers spent $108 million at local retailers, down from $111.9 million last year, representing a 3.4 per cent fall or 5.3 per cent with inflation taken into account.

The newly included data on “selected overseas declarations” by residents show a total of $20.4 million of goods brought in, equivalent to nearly one fifth of total sales at local stores.

These comprised $7 million declared by returning residents at LF Wade International Airport, $10.6 million brought in by courier, $2.2 million by sea and $0.6 million brought in via the Post Office.

The release shows figures for every month during the past year for these categories. The $10.6 million of goods brought in by courier matched the figure for December 2017. Imports via courier peaked at $12.6 million in April.

Walton Brown, the Minister for the Cabinet Office, said: “The December 2018 Retail Sales Index publication now shows categories of selected overseas declarations that represent a combination of goods purchased directly from overseas, online shopping, gifts, etc.

“Declarations by returning residents via the airport declined 4.1 per cent to $7 million. However, imports by households via sea more than doubled to $2.2 million.” He added that imports via courier and via the Post Office remained unchanged from December 2017.

Retailers of building materials recorded a 16.3 per cent decline in both sales volume amid lower demand for supplies and materials for construction projects.

Apparel stores suffered a nearly equally sharp decline, experiencing a 15.2 per cent contraction to December 2017.

Sales volume fell 7.8 per cent for motor vehicle sellers, 4.4 per cent for liquor stores, 2.7 per cent for food stores and 3.1 per cent for service stations.