Or rather, the economic weather coming out of China, which has been somewhat cloudy lately.
So news that Chinese factory output fell by more than expected in November is another disappointment for both stocks. The Chinese housing market and related sectors such as steel and cement manufacturing are both in decline, hitting demand for natural resources.
As if that wasnt enough, as Australias biggest oil exporter, BHP Billiton has also been knocked by the plunging oil price.
No wonder its share price has fallen off a cliff in the last three months, down 18% in that time. That is twice the 9% drop suffered by Rio over the same period.
This isnt a temporary slump but a long-term malaise, as five-year performance figures reveal. In that time, BHP Billiton has dropped nearly 25%, while Rio Tinto is down more than 10%.
This sector has been losing you money longer than you think.
Existing investors can hang on hoping for a reversal. New investors could even dive in, hoping to make a contrarian splash. The valuations look tempting, with BHP trading at less than nine times earnings, and Rio just over 13 times.
Both are now dividend income machines, yielding 4.82% and 4% respectively. Thats quite a turnaround for companies that were originally seen as a play on fast-growing emerging markets.
Both BHP and Rioare well managed, and have been diligently cutting costs, reducing exploration spend, boosting cash flow, and ramping up production.
But investors need to ask themselves this question: what on earth has happened to the much-vaunted commodity supercycle?
By taking copper and iron ore production to new highs despite falling prices, BHP Billiton and Rio Tinto are either pretending the supercycle is still spinning, or playing a Saudi Arabian-esque game of taking a short-term hit, knowing that higher-cost, lower-output rivals will take a far bigger hit in the longer run.
Its Gonna Rain
Its a dangerous game to play. Especially with Chinese GDP growth down to 7.3%, the lowest since the financial crisis. The real figure may be lower than that.
The sun could shine on BHP Billiton and Rio Tintos favour on Thursday, if European Central Bank president Mario Draghi finally unleashes QE on an expectant world.
If he doesnt, investors could face more heavy weather in 2015.
BHP Billiton and Rio Tinto won’t make you rich over the past five years, but plenty of FTSE 100 companies will have boosted your wealth over that time.
If you adopt the right investment strategy, you couldalsojoin the growing number of surprise UK millionaires who earned their wealth on the stock market.
To find out how stocks and shares can make you rich over the longer run, read this FREE Motley Fool report 7 Simple Steps For Seeking Serious Wealth.
Itwon’t cost you a penny to download, so click here now.
Harvey Jones has no position in any shares mentioned. The Motley Fool UK has no position in any of the shares mentioned. We Fools don’t all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors.