'The Mythical Phillips Curve?'

An entry in the ongoing debate over the Phillips curve:

The mythical Phillips curve?, by Simon Wren-Lewis, mainly macro: Suppose you had just an hour to teach the basics of macroeconomics, what relationship would you be sure to include? My answer would be the Phillips curve. With the Phillips curve you can go a long way to understanding what monetary policy is all about.

My faith in the Phillips curve comes from simple but highly plausible ideas. In a boom, demand is strong relative to the economy’s capacity to produce, so prices and wages tend to rise faster than in an economic downturn. However workers do not normally suffer from money illusion: in a boom they want higher real wages to go with increasing labour supply. Equally firms are interested in profit margins, so if costs rise, so will prices. As firms do not change prices every day, they will think about future as well as current costs. That means that inflation depends on expected inflation as well as some indicator of excess demand, like unemployment.

Microfoundations confirm this logic, but add a crucial point that is not immediately obvious. Inflation today will depend on expectations about inflation in the future, not expectations about current inflation. That is the major contribution of New Keynesian theory to macroeconomics. ...[turns to evidence]...

Is it this data which makes me believe in the Phillips curve? To be honest, no. Instead it is the basic theory that I discussed at the beginning of this post. It may also be because I’m old enough to remember the 1970s when there were still economists around who denied that lower unemployment would lead to higher inflation, or who thought that the influence of expectations on inflation was weak, or who thought any relationship could be negated by direct controls on wages and prices, with disastrous results. But given how ‘noisy’ macro data normally is, I find the data I have shown here pretty consistent with my beliefs.