The sow's ear effect is a term used in economics to describe when a country is unable to raise its productivity or per capita gross domestic product relative to other countries of similar development despite adjustments in macroeconomic policy, such as the exchange rate or the interest rate. This is due to deficiencies on the supply side of the economy. This could be for reasons such as a poorly skilled labour force.
The term sow’s ear comes from the phrase: You can’t make a silk purse out of a sow's ear.