For the five years I lived in and reported from China, it was the story that tied so many other stories together: Deng Xiaoping's 1980 decree that Chinese families could only have a single child.
It was the reason that a tragedy, like the 2008 Sichuan earthquake, felt more tragic – the knowledge that the children lost were often the only ones their parents would have. It was the law that made blind lawyer Chen Guangcheng into a dissident (he exposed forced abortions connected to the implementation of the law), eventually propelling him into exile.
It was the unspoken reason China has such a glut of men – gender-selective abortions created a gender ratio of 118 men per 100 women – and the reason stressed-out Chinese students felt such pressure to succeed, knowing they would have to take care of both their parents on their salary alone. The demographic time bomb the law implanted in Chinese society was the biggest reason to worry about the future of the world's second-largest economy, and thus our own.
The one-child policy was a three-word answer to anyone who tried to argue that China's rulers were not the tyrants they used to be. It was the Communist Party's ultimate intervention into the lives of the 1.4 billion people it ruled.
And now, it's over.
Thursday's bulletin on the official Xinhua news wire was as simple and direct as it was world-changing. "China abandons one-child policy, allows two kids for all couples," read the headline on its Twitter account. A brief news report added that the decision was made "to improve the balanced development of population."
While Communist Party communiqués are often long and torturously worded exercises in illogic, this one needed no explanation. Everyone knew it needed to happen. The only question was when.
The one-child policy was that rare issue that united Communist Party elders, who felt that the policy had served its purpose and it now was harming the country's future prospects (a 2010 census predicted that 2015 would be the year China's population would start to shrink), and young "netizens" who railed online against the government telling them how many children they could have.
An increasing number of Chinese went to extreme lengths to get around the policy. Those rich enough travelled abroad to give birth, or stayed in China and paid fines that were often several times the average annual income. Those less affluent resorted to tricks like fostering out some of their children to neighbours and relatives. There were horror stories, such as the 2012 case of a 23-year-old woman who – seven months pregnant with what would have been her second child – was strapped to a bed and forced to take an injection that induced early labour the baby was never meant to survive.
As far back as 2009, government experts were telling me that the one-child policy would soon be history. "The country's leadership realizes the problem. In China, most of the experts in population research have already suggested [changing the one-child policy] There is a consensus among scholars on the subject," said Zhou Haiweng, a population expert at the Shanghai Academy of Social Sciences. Shanghai is a rapidly aging city, where a third of the population will be 60 or older by 2020.
Mr. Zhou predicted when we met that the one-child policy would come to an end in 2011, when the government rolled out its blueprint for the coming five years. But then-president Hu Jintao – who will be remembered, if at all, as perhaps the weakest leader Communist China has had – was silent on the subject right up until his retirement in 2013, although the number of loopholes in the law was expanded (there were always exceptions for rural families, if their first child was a daughter, and for ethnic minorities). The logic remained that ending the one-child policy altogether would be an admission that Mr. Deng, his mentor, had erred back in 1980.
Instead, ending the one-child policy will be a reform attributed to President Xi Jinping, who is as powerful and popular as Mr. Hu was weak and bland. It will be part of his five-year plan, rather than Mr. Hu's.
Mr. Xi has in many ways been a disappointment this far. Despite hopes that he would follow his father – who was seen as a reformer within the Communist Party, and one of the few party elders who opposed the bloody 1989 crackdown on Tiananmen Square – there is no more freedom of expression, religion or association in today's China than when Mr. Xi became "paramount leader" two years ago. Nobel Peace Prize winner Liu Xiaobo remains in prison and incommunicado.
But if there was a list of human-rights issues any Chinese leader needed to address, ending the one-child policy was surely at the top.
And any biography of Mr. Xi will now mention high up that he was the president who finally struck down the hated rule. Being the man who ended 35 years of dubious and sometimes violent social engineering is a pretty good line to have on your resumé.