What does the infant mortality rate measure?

The infant mortality rate specifically measures the total number of deaths among infants under one year of age for every 1,000 live births in a given population during a specified time period, usually a year. This statistic is crucial for understanding the health and well-being of a population, as it reflects the overall quality of healthcare, maternal health, and the socio-economic conditions affecting families. High infant mortality rates can indicate issues such as inadequate healthcare systems, poor maternal nutrition, or environmental factors that could be detrimental to infant health during the early stages of life.

The other choices do not accurately define the infant mortality rate. The average lifespan of infants refers to expecting how long infants live, which is different from measuring mortality rates. The crude death rate for children under five encompasses a wider age range that includes toddlers and young children, not just infants. Lastly, the percentage of infants that survive past their first year reflects survival rates rather than the rate of mortality, which is specifically concerned with the number of deaths that occur. Therefore, the correct answer accurately captures the definition and significance of the infant mortality rate.