SINGAPORE — Policy makers in Asia grappling with how to measure the growth of e-commerce just scored one more tool in Singapore.

The Singapore Department of Statistics has started publishing the proportion of the city state’s retail sales that were transacted online. In February, those purchases made up 3.9 percent of overall retail sales, or S$144.3 million ($110 million), compared with 4.1 percent in the prior month, the agency reported Thursday.

That share appears unremarkable, and two months can’t qualify as robust data. But the gauge should prove to be a useful tool as officials across the region struggle to measure the impact of digital sales on their economies, and whether that should in turn prompt changes to tax policy.

Central banks and statistics agencies across Asia have been hiring armies of number-crunchers to explore how consumers’ shopping habits are affecting inflation.

In Southeast Asia specifically, online shopping is set to explode in the six biggest economies to $64.8 billion in 2021 from $37.7 billion last year, according to BMI Research calculations. A February report from Maybank Kim Eng Research Pte estimated Singapore’s online share of total retail sales at 5.4 percent, the highest among Southeast Asia’s five top economies. Malaysia was second, at 2.7 percent.

For a sale to be counted as “online,” the Singapore Department of Statistics said it verifies that an order and sale were conducted through a company’s website, third-party website, mobile application, extranet or Electronic Data Interchange. Payment may or may not have been made digitally.

By Michelle Jamrisko with assistance from Enda Curran; Editors: Nasreen Seria, Karthikeyan Sundaram.