Academic test-takers for the International English Language Testing System on the Chinese mainland improved in all four language skills from 2012 to 2018, according to a new IELTS white paper.

The average score for the test-takers on the mainland reached 5.72 points for the 2017-18 period, 0.16 points higher than the 2012-13 period, it said.

The white paper was released on Wednesday by the British Council, co-owner of the IELTS. The test is a comprehensive English proficiency assessment that focuses on four skills: listening, speaking, reading and writing, with maximum scores of 9 points each.

Reading scores improved the most, the white paper said, from 5.9 points in the 2012-13 period to 6.15 points in the 2017-18 period, while speaking scores only saw minimal improvement and only increased by 0.02 points during the same period.

The white paper is based on the results of all mainland IELTS test-takers from June 1, 2017 to May 31, 2018.

It also identified a gap between Chinese test-takers and global test-takers in overall performance on the IELTS academic module.

The main reason for the discrepancy lies in Chinese academic test-takers' poor performance in speaking, followed by writing and listening.

Chinese test-takers' reading performance has risen to the global average. Overall, the language output abilities (writing and speaking) of Chinese IELTS test-takers are weaker than their language input abilities (listening and reading). Data also shows that female test-takers generally achieved a higher score than males.

Candidates in Shanghai ranked first place in listening, speaking, reading and writing skills.

The white paper also said that undergraduate students continue to be the main group of IELTS test-takers on the mainland, accounting for 52 percent, while those under age 18 form the second-largest group, at 18 percent of the total.

Although 88.6 percent of the IELTS test-takers had overseas studies in mind - as the IELTS has been increasingly recognized by domestic schools and employers - there are an increasing number participating for various other purposes, including English proficiency testing, domestic college enrollment and job applications.

Chu Zhaohui, a senior researcher at the National Institute of Education Sciences, said the English proficiency of people in China has improved steadily thanks to education reforms adopted by the government and the opening-up of Chinese society.

However, proficiency in English varies greatly across the country. First-tier cities such as Shanghai and Beijing rank high because they are more engaged internationally, he said.

"The challenge is how we bring the rest of the country with them and what can we do nationally to lift everybody to the same kinds of opportunities for language learning. That's a big policy, investment and innovation challenge," Chu said.