Having spent five years in China, American journalist Roseann Lake decided to take a closer look at "leftover women — a term most notably used in China, which classifies women who remain unmarried into their late 20s and beyond.

The term has been widely used in China's media and has been the subject of magazine and newspaper articles, television series and books, focusing on the negative connotations and later positive reclamation of the term.

Lake first noticed the phenomenon during the first Chinese New Year she spent in China, working as a television reporter in Beijing.

After her female colleagues, who ranged in age from 24 to 27, returned to work after the new year's gatherings with families, they seemed depressed because of the pressure put on them by their families to get married.

Lake saw passionate, highly educated young Chinese women acquiring wealth, property and a measure of independence in record numbers.

Yet while they ascended in their careers, many struggled to find suitable romantic partners, despite an overwhelmingly large male population and immense traditional, parental and societal pressures to wed.

Lake writes that she "struggled to understand how this was happening in modern China".

Intrigued by the topic, Lake began researching the social and historical factors shaping the destinies of Chinese women. And the result is a book Leftover in China: The Women Shaping the World's Next Superpower.

The book takes a nuanced look at how marriage policies and patterns are at the heart of the cultural disconnect that animates much of the tension between old China and new China.

Lake discussed her work in a video on the book's web page.

Forty years ago, China started its one-child policy, and boys were preferred, especially in rural areas. But the majority of girls born then were in urban areas, where parents were more open-minded.

The parents would give the girl "every single resource that we have, and we are going to raise her as if she were a son, and it just so happened that she's growing up during a very prosperous time for China economically", Lake explained.

Lake said a population of men in rural areas who were left out of that economic growth "are certainly not compatible with these women", adding that China will have a surplus of 30 million marriage-age men by 2020.

Lake explained that things get more complicated "when you think that China is a traditional society in the sense that men usually married down and women marry up".

"If you are a woman in China, you are supposed to marry someone taller, more educated, with a higher salary," she said.

"(However), women in their own right have achieved so much and have accomplished so much that it's actually hard to find who's above them," she added.

Leftover in China combines reporting with historical and demographic research and scores of touching and humorous, real-life anecdotes from colleagues and friends.

Many of these women have started to stand up to shake the "leftover" label.

Contact the writer at xiaohong@chinadailyusa.com