ANALYSIS: For most of the past two decades, China - with 400 million middle-class consumers growing richer by the day - was a one-way bet for the world's corporations and a driver of the global economy.

By early 2018, General Motors was selling a third more cars in China than in the US. Starbucks unveiled plans to open a new coffee shop in China every 15 hours on average. Adidas saw 26 per cent growth in China while Western Europe, its home market, was staying flat or shrinking.

But what happens when the Chinese growth juggernaut slows? Or worse yet, grinds to a halt?

Andy Wong A woman browses her iPhone as she walks by a mural depicting an iPhone and Chinese people buy smartphone to communicate with family members, at a subway station in Beijing.

The world got a glimpse on Wednesday when Apple, the second-largest public tech company, lowered quarterly sales estimates for the first time in more than 15 years. Chief executive Tim Cook blamed the unforeseen "magnitude of the economic deterioration" in China, the world's largest smartphone market. Apple shares plummeted nearly 8 per cent in after-hours trading and pulled down a bevy of consumer stocks with exposure to the Chinese market.

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While a number of factors may have played into Apple's travails, including political tensions and a trade war with the United States, the news from Cupertino seems to affirm a warning that Chinese economic observers have been sounding for years, particularly in the last few months: the slowdown in China's economy might be worse than many appreciate - and so, too, are the spillover effects.

NG HAN GUAN/AP Apple's US$1,000 iPhone is a tough sell to Chinese consumers who are jittery over an economic slump and a trade war with Washington.

"China's economy is definitely slowing quite a bit across a bunch of sectors, and this slowing momentum is likely to continue for another couple of months at least," said Arthur Kroeber, the founder of Gavekal Dragonomics, a research firm in Beijing. "And consumer confidence is definitely down, which is probably part of what's behind the Apple numbers."

After multinational companies relied heavily on China for years for growth, warning signs across different industries are beginning to crop up suggesting there are broad, ominous trends gathering force in the world's second largest economy. In that regard, Apple isn't alone.

Months after Starbucks announced a massive China expansion this year, it said that China sales would increase just 1 percent, far below those in the United States. Jaguar Land Rover briefly shut a factory in Britain after September sales in China dropped by a half. LVMH, the luxury giant that owns Louis Vuitton and has often been used as a barometer for consumer spending in China, said the Chinese were spending "a little bit less."

Ng Han Guan Customers visit an Apple store in Beijing, China. The tech giant became the latest global company to collide with Chinese consumer anxiety when CEO Tim Cook said iPhone demand is waning, due mostly to China.

The significance of Apple's results is partly that it sheds a tiny bit of light on what's really going on in China - and how that might affect other firms and economies - in a country where top-line economic data given by the government are murky at best and fudged at worst.

Although Chinese officials report that GDP have been growing at more than 6 per cent a year for a few years, "it looks truly like some sixth grader got out their ruler and drew a straight line with a slight downward slant," said Christopher Balding, an expert on the Chinese economy at Fulbright University in Vietnam. "It's totally unrealistic."

As worries have mounted in recent months, top financial regulators have held meetings with economists at banks and brokerages to instruct them to take into account the interests of the Communist Party when they publish economic analyses - an apparent euphemism for holding back alarming language, Bloomberg reported in November.

But over the past 12 months, bits and pieces of data coming out have been precisely that: alarming.

Car sales have been shrinking for the first time since 1990, when most of the country was peddling bicycles. A key manufacturing survey at the end of the year showed Chinese factory activity actually contracting. And revenue from consumption tax was down 72 per cent in November from a year ago, Balding said.

Chinese investors have been among the most pessimistic about their economy's prospects: China's stock market lost US$2.3 trillion, or about a quarter of its value, in 2018 - its worst performance in a decade.

To be sure, Apple - perhaps the preeminent symbol of corporate America's success in China - is buffeted by forces far beyond the country's macroeconomic trends. Tech analysts say local brands like Huawei and Oppo have been closing the gap with Apple in terms of performance and design even while Cupertino continues to raise its prices.

Meanwhile, the US arrest warrant for Huawei chief financial officer Meng Wanzhou, who has been detained for the past month in Canada, infuriated many Chinese and touched a nerve in a country where nationalism - and distaste for the United States - has been on the rise as national competition has broken out.

In recent weeks, Chinese media have reported stories of companies awarding stipends to employees who ditch their iPhones to buy Huawei, said Shen Dingli, a well-known international relations commentator in Shanghai.

"The ordinary people may have a kind of nationalist consciousness," Shen said, adding that middle and upper class Chinese are no longer dazzled by iPhones like they were a decade ago. Apple's glory days are past," he said.

On Thursday, Henry Zhu, a student from Shenzhen, was browsing a Xiaomi store at the upscale Parkview Green mall in Beijing as he considered the relative attractiveness of Apple's latest products.

His very first smartphone was an iPhone 6, he said, but he has since switched to Chinese brands because of its similar quality and lower price. Now an iPhone X in China is twice the price of his Chinese-made OnePlus handset costing less than US$500. That just wasn't worth it when money is tight, he said.

"If I have more money to spare, maybe I won't hesitate to buy the latest iPhone," Zhu said as he brandished his bezel-less OnePlus 6, which, except for the logo, looked almost exactly like an iPhone. "For now, I'm happy with what I've got."