The number of registered volunteers reached 169 million by the end of last year on the Chinese mainland, a 13.9 percent increase year-on-year, according to the Blue Book of Philanthropy released on July 26.

The report, released by the Chinese Academy of Social Sciences, the Social Sciences Academic Press and the China Lingshan Council for the Promotion of Philanthropy, said the volunteers together offered more than 2.2 billion hours of service in 2019.

The report said the volunteers assisted in health, education, poverty alleviation, eldercare, environment, disability, culture and sports, among other areas.

Services related to the Belt and Road Initiative were also a favored area for volunteers last year, it added.

The growing volunteerism among the public came as China recorded a small decline in charitable resources－composed of public donations, the value of volunteer work and revenue from lotteries.

According to the blue book, China recorded 337 billion yuan ($48 million) in charitable resources last year. The number was 340 billion yuan in 2018 and 321 billion yuan in 2017.

The value of volunteer work was estimated at 90.3 billion yuan ($12.8 billion), increasing 9.7 percent year-on-year. That is more than twice the growth rate of public donations, which were estimated at 133 billion yuan last year.

However, the revenue from the China Sports Lottery and the China Welfare Lottery－two of the few legal avenues for betting in the country and a major source of traditional charity income－dipped by more than 13 percent year-on-year.

The blue book also shed light on some of the challenges facing the promising sector.

More than 87 percent of voluntary groups were grappling with various degrees of inadequate funding last year, double the ratio in 2018, the report said, pointing to the explosive growth of volunteers as a possible explanation.

Further, more than 40 percent of such groups reported last year that they could not find volunteers that suited their posts, compared with just 23 percent in 2018, and more than 30 percent of the organizations said local governments or neighborhood authorities were not supportive of their work, the report added.

In 2017, China rolled out the Voluntary Service Ordinance, the first legal provision dedicated to safeguarding the rights of people involved in voluntary work and establishing standards in a field that has expanded rapidly in the past decade.

To maximize the value of voluntary work, the rules encourage government agencies, businesses and NGOs to recruit volunteers who can provide skills-based services.

The concept of voluntary work was almost unknown on the mainland four decades ago, when China embraced reforms and a market economy.

The year 2008－which saw the Beijing Olympics and an earthquake in Sichuan province that left almost 70,000 people dead and nearly 20,000 missing－was considered a landmark in the development of the voluntary sector. That year drove the growth of volunteerism, NGOs and other charitable acts.