In this paper we explore the role of the sectoral composition of gross domestic product (GDP) in explaining the behaviour of youth labour markets. We provide a comparison of the behaviour of youth unemployment rates, employment-population rates, and labour force participation rates between developing countries and developed (rich) countries. In developing countries, open unemployment is less of a problem: the major problem faced by young people is employment in the informal sector that is poorly paid, intermittent, and insecure. A major part of employment in developing countries consists of "vulnerable employment". After a brief review of the literature, the paper uses panel data to estimate equations for unemployment rates, employment-population rates, and labour force participation rates for youths. We find that the sectoral composition of production and aggregate demand are important in explaining the behaviour of youth labour markets.