Long-run cross-country price data exhibit a puzzle. Today, richer countries exhibit higher price levels than poorer countries, a stylized fact usually attributed to the Balassa- Samuelson effect. But looking back fifty years, this effect virtually disappears from the data. What is often assumed...

This paper explores the implications of Unified Growth Theory for the origins of existing differences in income per capita across countries. The theory sheds light on three fundamental layers of comparative development. It identifies the factors that have governed the pace of the transition from...