The total fertility rate in an economy is defined as:

The correct definition of the Total Fertility Rate (TFR) is D) the average number of live births a woman would have by the end of her child-bearing age.

Let's look at the other options:

• A) The number of children born per 1000 people in the population in a year: This describes the Crude Birth Rate (CBR).
• B) The number of children born to a couple in their lifetime in a given population: This is a less precise definition and can be confused with TFR, but TFR specifically aggregates across all women in a population, assuming current age-specific fertility rates persist, and refers to a woman's lifetime.
• C) The birth rate minus death rate: This calculates the natural growth rate of a population.

TFR is a hypothetical measure that represents the average number of children that would be born to a woman over her lifetime if she were to experience the exact current age-specific fertility rates through her childbearing years, and she were to survive throughout her childbearing years. It's a standard demographic indicator used to assess fertility levels and future population trends.