China’s retail sales grew at 13.2% in July, year on year, a slowdown from 14.3% annual growth in 2012, and 17.1% growth in 2011. Sales of gold and silver jewelry rose 42% year on year in July.

Samsonite said its China revenue increased by an annual 8% in the first half of 2013, excluding the effect of currency gains. In the whole of 2012, the Hong Kong-listed luggage maker reported a 20% increase in China revenue.

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Want Want China reported revenue growth of 14.9% year on year in the first half of 2013, below the 19.4% growth it recorded in the first half of 2012. The food producer’s core dairy and beverage segment grew 18.3%, it said this week, compared with 28% in the same period a year earlier.

It’s not just premium brands that are reporting slowing revenue growth in the People’s Republic. Retail sales in almost every category are increasing more slowly than they were a year ago. Growth in cosmetics sales has slowed from 15% to 10%, and knitwear from 18% to 12.5%. Only gold and silver jewelry, which has a speculative appeal, has been gaining momentum, with sales up 42% year on year in July. Tiffany (TIF) says its China sales are “especially strong”.

This is happening at the same time China’s banks reported a sharp rise in bad loans from the retail and wholesale sector in their interim earnings. China Merchants Bank said non-performing loans to retail-sector companies increased by 48%. At China Construction Bank the increase was 19%, and at China CITIC Bank 66%.

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Retail revenue cannot expand at double-digit rates indefinitely. But growth expectations are important for retailers deciding how much capital to tie up in stocks and new stores. The increase in bad loans to the retail sector suggests that some operators overestimated demand. Sportswear maker Li Ning was an early warning of what can happen — it stuffed its retailers with unsaleable stock, and was forced to buy heaps of the stuff back to salvage its brand.

For some products like designer bags and spirits, government curbs on gift-buying are a factor. But that’s not enough to explain the broad slowdown. More likely, decelerating investment in housing, infrastructure and manufacturing, is dragging on incomes. Disposable per capita income for city-dwellers grew an annual 9% in the first two quarters of 2013, according to an official survey by the National Bureau of Statistics — compared with a five-year average of 13%.

If investment slows, then, so does consumption. That means China can’t rely on consumers to step up and fill the gap if investment levels fall, as eventually they must. It also makes the task of increasing China’s share of consumption in GDP from its low level of 35% that bit harder. If China wants consumers to pull their weight, it needs to put more money in their wallets.

Read more at Reuters Breakingviews.