How does sectoral change enhance development?

The Lewis Model argues economic growth needs structural change into the economy whereby surplus labour into traditional agricultural sector along with zero marginal products that migrate to the modern industrial sector, here their marginal product is much higher.

The Rostow model classifies a progression through primary orientated production along with low value added to manufacturing and services along with high value added.

Shifting resources through low productivity primary zone to higher productivity sectors increase output and income.