It has been nearly seven months since a young student was gang-raped in the New Delhi, India, and died from her horrific injuries 13 days later on December 29, 2012. The fast-track trial of the accused men has just re-started and the sentence is due any day now.

When thousands of Indians took to the streets to protest the inability of the establishment to protect women, they demanded not just a change in the law but in people's attitudes. But the watershed moment that many Indians hoped for doesn't seem to have arrived. And that may be because most Indians don't even recognise the extent of the problem in their own country.

Let's start with a figure: 60 million. That is nearly the entire population of the United Kingdom. That is also the approximate number of women "missing" in India. They have either been aborted before birth, killed once born, died of neglect because they were girls, or perhaps murdered by their husband's family for not paying enough dowry at marriage.

So why isn't there more recognition of this mass tragedy?... many Indians don't want to recognise the problem because it has become deeply ingrained in the culture.

That number isn't a wild exaggeration or a figure thoughtlessly plucked out of the air, but a matter of demographics. As far back as 1991, the economist Amartya Sen pointed out that Asia was missing 100 million women because of sex-selection and the poor attention paid to women. In 2005, it was estimated at 50 million Indian women in the New York Times. But this isn't a new problem.

In 1991, the Indian census showed an unprecedented drop of women in the sex-ratio. After running tests to check whether women had been under-counted, they found that a massive explosion in sex-selection during the 80s had led to a sharp drop in the number of girls being born. A report by Action Aid in 2009 ("Disappearing Daughters" [PDF]) found that in some villages in the state of Punjab, there were as few as 300 girls for every 1,000 boys.

Overall, India had 37.25 million fewer women than men according to the 2011 Census. To match the sexes equally and then increase the number of women to match the natural sex-ratio would require around 60 to 70 million women. That is the number of women missing. This phenomenon cannot be called anything less than genocide.

So why isn't there more recognition of this mass tragedy? In my recently released e-book India Dishonoured: Behind a Nation's War on Women, I show that many Indians don't want to recognise the problem because it has become deeply ingrained in the culture.

This is illustrated with how the political establishment reacted to the gang-rape in New Delhi. Initially, many politicians simply dismissed the protests on the streets. Mohan Bhagwat, chief of the powerful Hindu nationalist organisation Rashtriya Swayamsevak Sangh (RSS), even said, "You go to villages and forests of the country and there will be no such incidents of gang-rape or sex crimes. They are prevalent in some urban belts." He went on to criticise "western lifestyle" in cities for sexual assaults.

Even the prime minister said nothing about the incident until a week later, despite the protests. Nevertheless an independently produced report commissioned by the government made excellent recommendations that were broadly adopted despite some exceptions. Marital rape, for example, is still legal there.

While changes in the law are welcome, they barely scratch the surface. India and China alone represent nearly four out of every ten of all people on earth. Due to endemic sex-selection in both countries, the imbalance of women and men there is unprecedented in human history.

Unless the country recognises the gravity of the problem and does more to protect half the population, the social impact will be felt in every aspect of Indian society for decades.

In India, the overall sex-ratio for young children has fallen to 916 girls per 1,000 boys, and had consistently gotten worse over the last 60 years. In 2012, India was named the worst G20 country to be a woman in due to sex selection, infanticide and trafficking.

Worse, the liberalisation of social attitudes and rising incomes over the last 20 years has, paradoxically, made the matter worse in many ways. While some Indian women have never had so much freedom, these changes are being accompanied by a huge backlash in the form of higher rates of rapes and assaults, and an establishment that has preferred to blame "western values" instead.

But the problem in India goes to the heart of cultural practices that have been around for centuries. Culture doesn't just determine a country's laws and how well they are implemented, it also discourages or encourages violence against women. Practices such as paying dowry for brides, shunning divorced women, passing on inheritances only to men, not putting girls through schools - are all part of the problem. As families get richer, there is more pressure to pay out bigger dowries for girls and they have more money to afford an abortion.

According to one estimate, by 2020 India will have an extra 28 million men of marriageable age. The social impact of such an imbalance is unprecedented in history, and India barely has a police force and judicial system that can cope with the current problem.

Unless the country recognises the gravity of the problem and does more to protect half the population, the social impact will be felt in every aspect of Indian society for decades.

Sunny Hundal is the author of the recently released e-book, India Dishonoured: Behind a Nation's War on Women and is a regular contributor to the Guardian and the New Statesman.