We use principal component analysis to create three indices that measure the economic development of eleven cities in the Guangdong–Hong Kong–Macao Greater Bay Area (GBA) over 2010–2019. The indices, composed of sixteen socio-economic indicators spanning five dimensions: macro, openness, consumption, human capital, and diversification, track individual cities and the whole region’s performance. The Economic Progress Index indicates that the GBA made great strides in all dimensions. The region went through a structural transformation toward services and became more diversified, as confirmed by the Economic Diversification Index. The Economic Convergence Index shows that the cities became more similar in the human capital and consumption dimensions, which is conducive to labor mobility and risk sharing in the region. A comparison with Yangtze River Delta and Beijing-Tianjin-Hebei confirms a rapid integration in the GBA in these two dimensions and calls for more collaboration to promote trade and FDI in less developed GBA cities.