IN 1886 THOMAS STEVENS, a British adventurer (pictured), set off on an unusual bicycle trip. He pedalled from the flower boats of Guangzhou in China's south to the pagodas of Jiujiang about 1,000km (620 miles) to the north. He was disarmed by the scenery (the countryside outside Guangzhou was a “marvellous field-garden”) and disgusted by the squalor (the inhabitants of one town were “scrofulous, sore-eyed, and mangy”). His passage aroused equally strong reactions from the locals: fascination, fear and occasional fury. In one spot a “soul-harrowing” mob pelted him with stones, bruising his body and breaking a couple of his bicycle's spokes. A century later the bike was no longer alien to China; it had become symbolic of it. The “bicycle kingdom” had more two-wheelers than any other country on Earth. Many of those bikes have since been replaced by cars—one obvious sign of China's rapid development. But even today the bicycle looms large in the battle for China's soul. For China's fast-diminishing population of poor people, bikes remain an important beast of burden, piled high with recycled junk. For China's fast-expanding population of city slickers, the bicycle represents everything they want to leave behind. “I'd rather cry in the back of your BMW than laugh on the back of your bicycle,” as China's material girls say. Some dreamers in government see a return to the bike as an answer to China's growing problems of prosperity—pollution, traffic and flab. The country's National Development and Reform Commission wants government officials to cycle to work one day a week, though only if the distance is less than 3km. Even if it is a fading symbol of Chinese society, the bicycle remains a tempting metaphor for its economy. Bikes—especially when heavily laden—are stable only as long as they keep moving. The same is sometimes said about China's economy. If it loses momentum, it will crash. And since growth is the only source of legitimacy for the ruling party, the economy would not be the only thing to wobble. From 1990 to 2008 China's workforce swelled by about 145m people, many of them making the long journey from its rural backwaters to its coastal workshops. Over the same period the productivity of the workforce increased by over 9% a year, according to the Asian Productivity Organisation (APO). Output that used to take 100 people in 1990 required fewer than 20 in 2008. All this meant that growth of 8-10% a year was not a luxury but a necessity.

But the pressure is easing. Last year the ranks of working-age Chinese fell as a percentage of the population. Soon their number will begin to shrink. The minority who remain in China's villages are older and less mobile. Because of this loss of demographic momentum, China no longer needs to grow quite so quickly to keep up. Even the government no longer sees 8% annual growth as an imperative. In March it set a target of 7.5% for this year, consistent with an average of 7% over the course of the five-year plan that ends in 2015. China has been in the habit of surpassing these “targets”, which represent a floor not a ceiling to its aspirations. Nonetheless the lower figure was a sign that the central leadership now sees heedless double-digit growth as a threat to stability, not a guarantee of it.

The penny-farthing theory

Stevens's 1886 journey across south-east China was remarkable not only for the route he took but also for the bike he rode: a “high-wheeler” or “penny-farthing”, with an oversized wheel at the front and a diminutive one at the rear. The contraption is not widely known in China. That is a pity, because it provides the most apt metaphor for China's high-wheeling economy.

The large circumference of the penny-farthing's front wheel carried it farther and faster than anything that preceded it, much as China's economy has grown faster for longer than its predecessors. Asked to name the big wheel that keeps China's economy moving, many foreign commentators would say exports. Outside China, people see only the Chinese goods that appear on their shelves and the factory jobs that disappear from their shores; they do not see the cities China builds or the shopping aisles it fills at home. But the contribution of foreign demand to China's growth has always been exaggerated, and it is now shrinking.

It is investment, not exports, that leads China's economy. Spending on plant, machinery, buildings and infrastructure accounted for about 48% of China's GDP in 2011. Household consumption, supposedly the sole end and purpose of economic activity, accounts for only about a third of GDP (see chart 1). It is like the small farthing wheel bringing up the rear.

A disproportionate share of China's investment is made by state-owned enterprises and, in recent years, by infrastructure ventures under the control of provincial or municipal authorities but not on their balance sheets. This investment has often been clumsy. In the 1880s, according to Stevens, China showed a “scrupulous respect for individual rights and the economy of the soil”. The road he pedalled took many wearisome twists and turns to avoid impinging on any private property or fertile plot. These days China's roads run straight. Between 2006 and 2010 local authorities opened up 22,000 sq km of rural land, an area the size of New Jersey, to new development. China's cities have grown faster in area than in population. This rapid urbanisation is a big part of the country's economic success. But it has come at a heavy price in depleted natural resources, a damaged environment and scrupulously disrespected property rights.

The imbalance between investment and consumption makes China's economy look precarious. A cartoon from the 1880s unearthed by Amir Moghaddass Esfehani, a Sinologist, shows a Chinese rider losing control of a penny-farthing and falling flat on his face. A vocal minority of commentators believe that China's economy is heading for a crash. In April industrial output grew at its slowest pace since 2009. Homebuilding was only 4% up on a year earlier. Things are looking wobbly. But China's economy will not crash. Like the high-wheeled penny-farthing, which rolled serenely over bumps in the road, it is good at absorbing the jolts in the path of any developing country. The state's influence over the allocation of capital is the source of much waste, but it helps keep investment up when private confidence is down. And although China's repressed banking system is inefficient, it is also resilient because most of its vast pool of depositors have nowhere else to go. Not so fast The penny-farthing eventually became obsolete, superseded by the more familiar kind of bicycle. The leap was made possible by the invention of the chain-drive, which generated more oomph for every pedal push. China's high-wheeling growth model will also become obsolete in due course. As the country's workforce shrinks and capital accumulates, its saving rate will fall and new investment opportunities will become more elusive. China will have to get more oomph out of its inputs, raising the productivity of capital in particular. That will require a more sophisticated financial system, based on a more complex set of links between savers and investors.

Other innovations will also be needed. China's state-owned enterprises emerged stronger—too strong—from the downsizing of the 1990s, but the country's social safety net never recovered. Thus even as the state invests less in industrial capacity, it will need to spend more on social security, including health care, pensions, housing and poverty relief. That will help boost consumer spending by offering rainy-day protection.

The chain-drive was not the only invention required to move beyond the penny-farthing. The new smaller wheels also needed pneumatic tyres to give cyclists a smoother ride. In the absence of strong investment to keep employment up and social unrest down, China's state will also need a new way to protect its citizens from bumps in the road ahead.