The disappointing payroll numbers in the United States out last Friday seem to suggest that the outlook for the US economy is not as rosy as expected.

Hiring by US employers last month had slowed to its weakest pace in six years - adding a mere 38,000 jobs - confounding expectations for growth of about 160,000. But stock markets still rallied as investors bought into the generally positive tone struck by US central bank chief Janet Yellen on the state of the US economy.

What also cheered investors was an indication from her that the Federal Reserve would hold back a further interest rate hike for now - a remarkable turnaround from the position taken by other top Fed officials who had been hinting as recently as two weeks ago that they were preparing to raise rates.

The bigger question is whether the world's No.1 economy is facing a new economic slowdown, or simply a blip.

Dr Yellen is upbeat on the US economy, noting that positive forces supporting job growth should outweigh negative ones.

But one of the biggest stock market puzzles in the past few months had been the disconnect between the buoyant US job market and the profit recession felt by US-listed companies.

In theory, more people get employed with increased job opportunities when companies expand and make more money.

Instead, US companies reported a 7.6 per cent drop in profits for the first three months of the year, as compared with last year, extending what amounted to four consecutive quarters of year-on-year declines in earnings. Thus, the dismal May job number is worrisome as it appears to confirm the trend of tepid corporate earnings, indicating that the US economy may be slowing down.

This unexpected turn of events also gives credence to the argument that depressing interest rates to almost zero and printing trillions of dollars to jump-start the economy are not working their magic.

Mr Raghuram Rajan, head of the Indian central bank and a former International Monetary Fund chief economist, asked if such loose monetary policies were also weakening the underlying performance of the economies they were supposed to help. The stimulus was supposed to "balance things out" when households and companies were being excessively cautious with their spending, "but eight years after the financial crisis, we have to ask ourselves: Is that the real problem?", he was quoted as saying by the Financial Times.

In a recent South China Morning Post article, Morgan Stanley's former chief Asia economist Andy Xie flagged a related problem - the massive factory overcapacity in China and the impact this will have on the global economy.

As major central banks depressed interest rates to almost zero, miners and oil companies had fuelled a huge commodity bubble by borrowing trillions of dollars to build new mines and oilfields. Their intention was to supply raw materials to China, which had raised credit spending by US$20 trillion (S$27 trillion) after the global financial crisis. That bubble has now burst as China's pace in infrastructural spending slowed down but the impact is only beginning to be felt.

He wrote: "The process of building a factory creates demand. But when it is completed, it needs to sell the goods to someone. What China did was to build even more factories to keep this factory occupied."

One fear is that China may try to export this overcapacity overseas, and because the slack is so huge, Mr Xie warned that it may kill capital expenditure in the rest of the world. The result would be a massive dampening of employment and income across the globe, triggering a wave of bankruptcies.

So, is the dismal US job data simply confirming what these doomsday economists are predicting? It is difficult to tell at this stage.

But the jubilation that stock markets are enjoying over the US Fed's decision to withhold further rate hikes for now may turn out to be short-lived if the job data turns out to be an early warning signal that the US is succumbing to the same sluggish malaise afflicting other major economies.

•Goh Eng Yeow will be hosting DBS chief executive Piyush Gupta to a chat on investments at the Singapore Coffee Festival on Saturday at 4pm. Get more details and tickets at http://sgcoffeefestival.com.sg