A spike in the yield for 5-year inflation-protected Treasuries yesterday preceded the plunge in oil prices (shown on the chart is Brent crude). Market chatter blames higher US supplies, and the news flow supports that interpretation. But the sharp rise in US “real” interest rates on the back of a stronger-than-expected employment report may have added to downward pressure. It isn’t just the United States: China and Germany are both alert to inflation tipping over the psychologically important 2% mark. The European Central Bank isn’t tightening credit any time soon, and the People’s Bank of China is putting only the slightest pressure on money markets to signal banks to restrain credit growth. But the prospect of a global tightening cycle is something that commodity investors will watch carefully. Although supply factors probably were the decisive factor in yesterday’s oil market, commodity markets may be highly sensitive to indications of possible stringency on the part of the major central banks.