Inflation

Demand-pull inflation

Demand-pull inflation is asserted to arise when aggregate demand in an economy outpaces aggregate supply. It involves inflation rising as real gross domestic product rises andunemployment falls, as the economy moves along the Phillips curve. This is commonly described as "too much money chasing too few goods". More accurately, it should be described as involving "too much money spent chasing too few goods", since only money that is spent on goods and services can cause inflation. This would not be expected to happen, unless the economy is already at a full employment level.

Cost-push inflation

Keynesians argue that in a modern industrial economy, many prices are sticky downward or downward inflexible, so that instead of prices for non-oil-related goods falling in this story, a supply shock would cause a recession, i.e., rising unemployment and falling gross domestic product. It is the costs of such a recession that likely causes governments and central banks to allow a supply shock to result in inflation. They also note that though there was no deflation in the 1980s, there was a definite fall in the inflation rate during this period. Actual deflation was prevented because supply shocks are not the only cause of inflation; in terms of the modern triangle model of inflation, supply-driven deflation was counteracted bydemand-pull inflation and built-in inflation resulting from adaptive expectations and the price/wage spiral.

Built-in inflation

The built-in inflation originates from either persistent demand-pull or large cost-push (supply-shock) inflation in the past. It then becomes a "normal" aspect of the economy, via inflationary expectations and the price/wage spiral. 

Inflationary expectations play a role because if workers and employers expect inflation to persist in the future, they will increase their (nominal) wages and prices now. (See real vs. nominal in economics.) This means that inflation happens now simply because of subjective views about what may happen in the future. Of course, following the generally accepted theory of adaptive expectations, such inflationary expectations arise because of persistent past experience with inflation. 

The price/wage spiral refers to the adversarial nature of the wage bargain in modern capitalism. (It is part of the conflict theory of inflation, referring to the objective side of the inflationary process.) Workers and employers usually do not get together to agree on the value of real wages. Instead, workers attempt to protect their real wages (or to attain a target real wage) by pushing for higher money (or nominal) wages. Thus, if they expect price inflation - or have experienced price inflation in the past - they push for higher money wages. If they are successful, this raises the costs faced by their employers. To protect the real value of their profits (or to attain a target profit rate or rate of return on investment), employers then pass the higher costs on to consumers in the form of higher prices. This encourages workers to push for higher money wages.