This article looks at how interest rates and inflation affect growth in the capital stock, labour supply, and technology, the main determinants of long-run economic growth. Many additional factors affect long-run economic growth, but most of these factors lie outside the sphere of monetary policy. Monetary policy therefore has only a limited capacity to contribute to economic growth over the longer term. However, the evidence does indicate that keeping inflation low and stable makes a positive contribution to long-run economic growth, and that this is the most effective contribution that monetary policy can make to the economy's performance over time. This finding supports the monetary policy framework operational in New Zealand, which is focused on keeping inflation between 1 and 3 per cent on average over the medium term.