This continues a pattern. Since 2008 there has been a significant correlation between breakeven inflation and the All-Share index: both fell in 2008-09, rose in 2009-10 and sagged between 2014 and February 2016.
However, this is only a recent development. For most of the 1980s and 1990s inflation was regarded as bad for equities; there was for years a strong correlation between inflation and the dividend yield, with higher inflation associated with lower equity valuations.
So what changed?
You might think it is the increased importance to the UK market of commodity stocks. These benefit from higher commodity prices, which are also associated with higher inflation expectations.
This, though, is no explanation. It merely poses the question: why don't commodity users (which are most stocks) lose from higher commodity prices? Yet they don't seem to: non-commodity stocks have shared in the rally since February.
Instead, there's another explanation. At low levels of inflation, the breakeven inflation rate is measuring not just inflation expectations but the risk of deflation. A rise in breakeven inflation from, say, 1.9 to 2.3 percentage points is therefore a good thing not because 2.3 per cent inflation is better than 1.9, but because it means the risk of deflation has fallen.
The market regards deflation as a nasty risk. Because interest rates cannot become sharply negative - at least without doing more harm than good - deflation implies rising real interest rates. That's a tightening of monetary policy. And it means real debt burdens increase; if prices fall, indebted companies must sell a greater volume of goods to service their debts. All this helps explain why companies have cut their debt in recent years despite low interest rates. It's because they don't want to enter deflation with high debt; since August 2008 non-financial companies' bank debt has fallen by 29 per cent, or almost £150bn.
This, I suspect, suggests that the link between breakeven inflation and share prices from now on might be asymmetric. A rise in breakeven inflation might have only a small effect because the shift from a small risk of deflation to a very small one is only a slightly bullish development. However, a fall in breakeven inflation might be bad news, to the extent that it puts the possibility of deflation back on the table.
In this sense, equity investors are vulnerable to a failure of economic policy. An expansionary fiscal policy and/or a 'helicopter drop' of money would almost certainly be inflationary - sufficiently so to remove the fear of deflation. With such policies off the agenda, however - in the eurozone as well as UK - the risk of deflation will remain, to the detriment of equities.
