Final answer:
The growth in the population over age 65 is a major factor affecting health care service delivery in the US. This demographic change, often referred to as the 'graying of America,' leads to increased demand for medical care and a rise in Medicare spending.
Step-by-step explanation:
A major factor affecting health care service delivery in the US is the growth in the population over age 65. This demographic shift is significant due to the increasing healthcare needs and the higher healthcare spending associated with the aging population. As the baby boomer generation, comprised of approximately 74 million people, has started to reach retirement age, there is a higher prevalence of age-related health conditions that require more intensive and prolonged healthcare services.
Moreover, the U.S. Census Bureau reported that as of 2013, 20% of the U.S. population was over 60 years old. This 'graying of America' suggests that a substantial portion of the population will require increased medical care, and it is projected that Medicare spending will rise significantly, reaching 15 percent of GDP by 2080. Additionally, advances in medical technologies and health reforms such as the Affordable Care Act have expanded access to health care, further increasing demand.