Image caption China's biggest matchmaking service, Baihe, has teamed up with Sesame

In most countries, the existence of a credit system isn't controversial. Past financial information is used to predict whether individuals will pay their mortgages or credit card bill in the future.

But China is taking the whole concept a few steps further. The Chinese government is building an omnipotent "social credit" system that is meant to rate each citizen's trustworthiness.

By 2020, everyone in China will be enrolled in a vast national database that compiles fiscal and government information, including minor traffic violations, and distils it into a single number ranking each citizen.

That system isn't in place yet. For now, the government is watching how eight Chinese companies issue their own "social credit" scores under state-approved pilot projects.

One of the most high-profile projects is by Sesame Credit, the financial wing of Alibaba. With 400 million users, Alibaba is the world's biggest online shopping platform. It's using its unique database of consumer information to compile individual "social credit" scores.

Users are encouraged to flaunt their good credit scores to friends, and even potential mates. China's biggest matchmaking service, Baihe, has teamed up with Sesame to promote clients with good credit scores, giving them prominent spots on the company's website.

"A person's appearance is very important," explains Baihe's vice-president, Zhuan Yirong. "But it's more important to be able make a living. Your partner's fortune guarantees a comfortable life."

Media playback is unsupported on your device Media caption The BBC's Celia Hatton spoke to consumers in Beijing to find out what they thought about the plans

More and more of Baihe's 90 million clients are displaying their credit scores in their dating profiles, doing away with the idea that a credit score is a private matter.

However, Sesame Credit will not divulge exactly how it calculates its credit scores, explaining that it is a "complex algorithm".

The company refused to give an interview to the BBC, citing concerns that the government would refuse to grant a permanent licence to issue credit scores if it engaged with the foreign media.

Instead, their spokeswoman issued a statement, discounting persistent rumours that the organisation monitors users' social media activity when assessing their social credit.

Sesame Credit tracks "financial and consumption activities of our users, and materials published on social media platforms do not affect our users' personal Sesame Credit score," explained spokeswoman Miranda Shek.

Image copyright Reuters Image caption Alibaba is the world's biggest online shopping platform

Sesame rates the online financial transactions of those using Alibaba's payment system, in addition to data it obtains from its partners including the taxi service Didi Kuaidi, rating whether users bothered to settle taxi payments.

Controversially, the company does not hide that it judges the types of products shoppers buy online.

"Someone who plays video games for 10 hours a day, for example, would be considered an idle person, and someone who frequently buys diapers would be considered as probably a parent, who on balance is more likely to have a sense of responsibility," Li Yingyun, Sesame's technology director told Caixin, a Chinese magazine, in February.

The Chinese authorities are watching the pilot process very carefully. The government system won't be exactly the same as the private systems, but government officials are certainly taking cues from the algorithms developed under the private projects.

Image copyright Getty Images Image caption Consumer spending is playing a growing role in the Chinese economy

A lengthy planning document from China's elite State Council explains that social credit will "forge a public opinion environment that trust-keeping is glorious", warning that the "new system will reward those who report acts of breach of trust".

Details on the inner workings of the system are vague, though it is clear that each citizen and Chinese organisation will be rated. A long list of people in certain professions will face particular scrutiny, including teachers, accountants, journalists and medical doctors. The special list even includes veterinarians and tour guides.

A national database will merge a wide variety of information on every citizen, assessing whether taxes and traffic tickets have been paid, whether academic degrees have been rightly earned and even, it seems, whether females have been instructed to take birth control.

Critics say the social credit system is "nightmarish" and "Orwellian". However, some believe that some kind of credit system is badly needed in China.

"Many people don't own houses, cars or credit cards in China, so that kind of information isn't available to measure," explains Wen Quan, a blogger who writes about technology and finance.

"The central bank has the financial data from 800 million people, but only 320 million have a traditional credit history."

'Very convenient'

Credit systems build trust between all citizens, Wen Quan says.

"Without a system, a conman can commit a crime in one place and then do the same thing again in another place. But a credit system puts people's past history on the record. It'll build a better and fairer society," she promises.

In a trendy neighbourhood in downtown Beijing, many were enthusiastic when asked about their Sesame Credit ratings, proudly displaying them on their mobile phones.

"It is very convenient," one young woman smiled. "We booked a hotel last night using Sesame Credit and we didn't need to leave a cash deposit."

Sesame has promoted the consumer benefits of a good credit score, from a prominent dating profile on the Baihe matchmaking site to VIP reservations with hotels and car rental companies. A mobile phone game designed by Sesame Credit encourages users to guess whether they have higher or lower credit scores than their friends, encouraging everyone to openly share their ratings.

But few people seemed to understand that a bad score could hurt them in the future, preventing them from receiving a bank loan or signing a lease.

And, even more concerning, many didn't know they were being rated by Sesame at all. For now, the pilot credit system is voluntary, though it's difficult to circumvent. Online shopping is a part of life in modern Chinese cities and Alibaba's financial payment service is ubiquitous.

"We repeatedly remind our customers that using Sesame Credit is voluntary," explains the matchmaking site's vice president, Zhuan Yirong.

"But people really care about trust and honesty. Alibaba's data can provide certain kind of proof. It's not 100% accurate, but at least it's one more filter for people to know each other better."

Perhaps it is good for all citizens to learn quickly about the concept of a "social credit" score, while it is still partly voluntary. Within five years, the government's mandatory system will rank everyone within China's borders.