2 billion women living in Asia are still paid less than men for similar work and are extremely underrepresented in top leadership positions, even in wealthy countries such as Japan, according to a report issued on Thursday.

The Asia Society survey on women's status in health, education, economic activity and political leadership urges improvements to ensure the region benefits fully from its underused pool of human talent.

While the status of women varies widely from country to country from one category to the next, overall, "to continue in this direction would put in peril Asia's many achievements," said the report, compiled by Astrid S. Tuminez, a professor at the Lee Kuan Yew School of Public Policy in Singapore.

Limits on female employment cost the region $89 billion a year in terms of lost productivity and human resources, the report said, citing United Nations data.

Overall, based on various measures - the report also uses data from The Economic Forum and other sources - the gender gap was narrowest and women's leadership strongest in New Zealand, Australia, the Philippines, Sri Lanka and Mongolia.

The gap was widest in Pakistan, Nepal, India, South Korea and Cambodia.

"Some economies in Asia with the highest human development rankings also perform most poorly in some measures of women's leadership," it said, referring specifically to Japan and South Korea.

Asia leads the world in terms of the number of years women have governed as heads of state, and currently has four women leaders. But the report attributes that to dynastic traditions calling for women to take over from fathers, husbands or sons when they die, are imprisoned or killed.

It said the problem begins before birth, with sex-selective abortions and infanticide due to a preference for sons in countries such as China and India.

It said the bias in favor of sons means that girls in some countries receive poorer medical care, nutrition and education than boys, especially in developing countries.

The discrepancy in schooling leaves the majority of women in four Asian nations illiterate, the report said, citing literacy rates of 10 per cent in Bhutan, 16 per cent in Pakistan, 25 per cent in Nepal and 31 per cent in Bangladesh.

Although women live longer in Asian nations as in other regions, such disadvantages affect health and earning power over a lifetime, the report noted.

"From the very start, girls in Asia face significant obstacles to fulfilling their human potential, in general, and their potential for leadership, in particular," Asia Society President Vishakha N. Desai said in introducing the report.

Pay gaps remain significant, the report said, with the ratio of women's pay to men's lowest in South Korea, at 51 per cent, below that of Nepal, Bangladesh and China. Japan's was not much better, at 60 per cent.

The narrowest gaps, the report found, were in Malaysia and Singapore, at 81 per cent, and Mongolia and Thailand, at just under 80 per cent. Globally, women's pay is 20 per cent to 30 per cent less than men's, on average.

As far as women in senior corporate positions, Japan came in worst in the region with just 5 per cent of those postions held by women.

Thailand and the Philippines ranked highest in this regard, with women holding 39 per cent of senior level positions, while India came in at 14 per cent and China 25 per cent, it said, citing a survey by human resources consultancy Grant Thornton International.

The percentage of women on corporate boards was much lower, with Japan at 0.9 per cent, South Korea at 1.9 per cent and China at 8.5 per cent. New Zealand ranked highest, at 9.3 per cent. The global average is 21 per cent, down from 24 per cent in 2009, the report said.

The report suggests specific countermeasures, such as providing more mentoring, more generous parental leaves, childcare and elder care, and gender-equal retirement packages would encourage women to persevere with their careers to top management positions.

But more fundamentally, it urges greater education aimed at valuing girls and women on a par with boys and men, steps to end sex selective abortions and improvement in women's property rights and other protections to ensure they can contribute fully to society.

The Asia Society, based in New York, is a global non-profit organization seeking to promote closer ties between Asia and the West through arts, education, policy and business outreach.