The ratio of economic yield to the biological yield is

The ratio of economic yield to biological yield is the Harvest index.
Harvest index (HI) is the ratio of grain to total shoot dry matter and is a measure of reproductive efficiency. HI is determined by interactions between genotypes (G), environment (E) and crop management (M).
Economic yield is the mass of desired product. The harvest index is calculated by dividing the dry mass of economic yield by the dry mass of biological yield.