A population pyramid, also known as an age-sex pyramid, is a graphical depiction used to study a country's Population. It uses age to connect the number of males and females in a population. The age group determines the number of dependents and economically active citizens in the Population. The pyramid's base is large and narrows at the top when a population's birth and death rates are high. The population pyramid is narrow at the bottom and expansive at the top when a country's Population has low birth and death rates. This is a pyramid that has been inverted.