Grantham had earlier warned of trouble if China quickly slowed its demand growth for minerals.

True: a Grantham or GMO publication or interview dated before January 2016 (e.g. 2011–2013 letters on commodities and China) warns that trouble would follow if China's growth in demand for minerals or commodities slowed quickly. Mostly true: an earlier warning about China's demand slowing and commodities exists, but it is worded somewhat differently (e.g. about commodity prices generally rather than minerals, or about a slowdown without 'quickly'). Mixed: his earlier writings discuss China's commodity demand only ambiguously. Mostly false: the earlier writings stress the opposite (sustained Chinese demand), with only a passing caveat. False: no prior warning appears in his letters, and his earlier writings expected China's demand to stay strong without such a warning.

Set before the research began.

1. E1 Bad China, good weather will bust commodity market 'en masse,' Grantham says InvestmentNews · 26 May 2011

   “In an April 25 letter to investors, Grantham said that a decline in China's economy would hurt the commodity markets. If a Chinese decline were accompanied by better-than-expected weather globally, then “it will very probably break the commodity markets en masse,” he wrote in the letter.”

2. E2 Bad China, good weather will bust commodity market 'en masse,' Grantham says InvestmentNews · 26 May 2011

   “Jeremy Grantham said there is a 25 percent chance that China, the world's second-largest economy, will “stumble” by next year over imbalances such as too much capital spending, an overheating real estate market or accelerating inflation.”

3. E3 Bad China, good weather will bust commodity market 'en masse,' Grantham says InvestmentNews · 26 May 2011

   “Despite some short-term shocks, global demand for energy, metals and crops is outpacing supply, Grantham said, creating “brilliant long-term prospects” for commodities.”

An independent May 2011 InvestmentNews report on Grantham's April 25, 2011 investor letter says he warned that a decline in China's economy would hurt commodity markets. Combined with better-than-expected weather, he wrote, this would "very probably break the commodity markets en masse" (E1). The same report says he put a 25 percent chance on China stumbling by the following year (E2). This is an earlier warning tying Chinese weakness to commodity trouble, but it speaks of a decline in China's economy and commodities in general, not a quick slowdown in China's demand for minerals. The same report also says Grantham described long-term commodity prospects as brilliant (E3); because the earlier warning in E1 is about a decline in China's economy hurting commodity markets rather than a quick slowdown in demand for minerals, the claim fits "mostly true" rather than "true" under the criteria.