Population pyramids can show differences in birth and death rates between more economically developed countries (MEDCs) and less economically developed countries (LEDCs). MEDCs typically have population pyramids with wide bases that taper at the top, showing low birth and death rates, while LEDCs often have bulging middles and bases, indicating high birth rates and high death rates among both infants and the elderly. Population pyramids provide a visual representation of a country's age structure and demographic trends over time.