We are passing through the Global Action Week (May 2-8), which is observed annually across the world to highlight the importance of "education for all".

Let us use this important occasion to take a closer look at this year's theme: Gender equality in education. Education leads to profound life-changing choices. But even in this advanced age, more than 39 million girls in the world do not have access to primary-level education and are thus denied this fundamental human right.

Inequality in education cripples the lives of millions of girls and women around the world. While women's rights have made significant progress, women are still second-rate citizens in a lot of countries. According to United Nations Population Fund (UNFPA) figures, women perform 66 percent of the world's work and help produce 50 percent of the global food output but earn less than 10 percent of the global income and own just 1 percent of the global property stock. Although the gender gap in education has narrowed over the past decade, girls are still at a disadvantage, especially when it comes to higher secondary education. Women in South Asia, for example, have only half as many years of education as men, and the female enrolment rate at the higher secondary level is two-thirds that of males.

The situation in China, however, is a lot more encouraging. The average years of education for women in 2008 was 7.3, only one year less than that of men. The gender parity index at the higher secondary level in 2009 was about 0.89, meaning that girls' participation at this level of education was comparable to that of boys.

Latest data of UN Educational, Scientific and Cultural Organization (UNESCO) show that in South and West Asia on average only one in two women can read and write. In stark contrast, about seven out of 10 men can do so. In East Asia and the Pacific, a staggering 74.5 million women are illiterate, representing 71 percent of the total 105 million illiterate adults.

China has made remarkable progress in literacy in the last 20 years. Its female illiteracy rate (15 year-old and above) dropped from more than 30 percent in 1990 to 11.52 percent in 2008, which has greatly contributed to the reduced number of illiterates, especially among women, in the Asia-Pacific region.

These issues are at the heart of UNESCO's mission, which is promoting quality education for all. This includes supporting quality education from early childhood through to primary and secondary levels, and up to the tertiary and vocational training levels. Achieving equality in primary and secondary education is critical to overcoming development challenges and structural discrimination. Education is critical to laying the foundation of gender equality and the empowerment of women. Even today, the fate of most women in many developing countries is to get married, become mothers when still very young and then tend to the family. This starts during adolescence when many girls are busy looking after their siblings, cooking and cleaning at home, and attending to other household chores, while their chances of going to school or receiving proper medical care are much lower than their male counterparts.

Adolescence is a critical stage. If a girl pursues the course dictated by poverty, she will be obliged to abandon her education and almost certainly get married at an early age. Statistics show that in developing countries 25 to 50 percent of girls become mothers before they reach the age of 18.

This is depressing because an uneducated mother, who does not have life and labor skills, is less likely to earn money and even less likely to stand up for her rights and influence the family or public life. Moreover, she will be more vulnerable to sexual violence and HIV infection. About 14 million adolescent girls become mothers every year, according to UNFPA figures. Complications during pregnancy or labor are the main cause of death of girls aged between 15 and 19 years. Adolescent girls are also two to five times more likely to die from pregnancy-related complications than women in their 20s, and their children are 1.5 times more likely to die before their first birthday. Each sad story, multiplied by millions of girls, consigns entire communities and countries to chronic poverty and poor health.

But there is an alternative. If a girl continues her schooling and learns life skills, she will marry later in life, have fewer and healthier children, and is more likely to earn a salary and send her children to school.

Investing in girls' education is the right, and the most important thing to do. Women represent half the population and "hold up half of the sky", as a Chinese leader said, and should have their rightful share in making decisions that affect their lives and countries. Women and girls are half of the human capital available to alleviate poverty and attain development. But without education they are unable to pursue these targets to the extent they should.

Investing in girls' education makes economic sense, too. Nationwide, each additional year of schooling raises average annual GDP growth by 0.37 percent. An added year of school increases a girl's eventual wages by 10 percent, reduces the probability of infant mortality by 10 percent and decreases female fertility rate by 10 percent. Moreover, women who earn money reinvest 90 percent of it in their families as opposed to 30 to 40 percent for men.

Therefore, investment in girls' education is possibly the best investment that people in the developing world can make. Girls are a powerful force of transformation and, if given the opportunity, hold the key to a better future. Let's use the occasion of Global Action Week to raise the critical need to invest our time, energy, thought and funding in girls' and women's education.

The author is director and representative of United Nations Educational, Scientific and Cultural Organization Beijing Office.