Robert Solow

Solow's 1956 growth model showed that in the long run, output per worker depends on technology and savings rate; capital accumulation alone produces diminishing returns. The Solow residual — typically 30-60% of output growth — is the share attributable to technological progress (TFP). The model predicts conditional convergence: poor countries with similar fundamentals catch up.

Solow's framework is the workhorse of African growth accounting (Hulten 2001, World Bank decomposition exercises). Most African TFP growth has been weak or negative in 1980-2010, with growth driven by factor accumulation; that's the diagnosis behind every 'productivity gap' policy discussion. Conditional convergence predicts African catch-up — but conditioning on institutions (Acemoglu 2024) and human capital tells us which countries are likely to make it.

Decompose any growth episode into capital deepening, labour quality, and TFP. If TFP is the laggard (typical for African growth), the policy fix is technology, not more investment.