BEIJING -- China's courier sector saw steady growth in May, according to an industry index released by the State Post Bureau Monday.

The express delivery development index stood at 472.9 in May, up 3.1 percent from the same period last year, according to the bureau.

Included in the figures, the sub-index for development scale rose 7 percent year-on-year, while service quality figures remained unchanged from a year earlier. The sub-index for development capacity increased 3.3 percent.

In May, the country's courier sector continued to expand in scale, with its increasingly diversified service system and upgraded facility networks playing a more prominent role in supporting the real economy, according to the bureau.

The index is compiled based on data from major logistics firms operating delivery services. It reflects overall business activities and trends in the country's courier sector.