An understanding of the past helps us to prepare for the future. In this, the REAL Centre's first report, we look back at the care and treatment provided by the NHS in England over the past two decades-as measured by health care activity. Measures of activity-what the NHS does-form the basis of much NHS planning. Together with measures of quality, these are used as proxies for understanding the contribution the NHS makes to population health. Understanding the drivers of this activity is therefore crucial to service and resource planning. In this report, we provide a framework for understanding the drivers of health care activity. We describe how supply and demand side factors interact, and how policy can influence the care the NHS provides. We look at the overall trends in activity and how specific services have changed. Where possible, we estimate the proportion of any change that can be explained by four demographic factors: population size, age, gender, and proximity to death. We then explore what drives the remaining change, unexplained by demography. Although we focus on England, many of the lessons may be relevant to the other countries of the UK. We take an in-depth look at emergency and planned hospital care, mental health, community and primary care, but do not look in detail at areas such as high cost drugs or highly specialised services. Social care, too, is beyond the scope of this initial report but will be the focus of subsequent analysis by the REAL Centre. * This is cost-weighted. See section 3 for further detail. The bigger picture: learning from two decades of changing NHS care in England seen between services, combined with changes to the cost of different activities, have produced a major shift in the composition of spend towards hospital-based care and away from other areas. The expansion in activity means the population receives significantly more health care today, which has contributed to lower mortality rates for a range of conditions and, up until 2010, increasing life expectancy. However, improvements and increases in care have not been uniform over the past two decades. Between 2000/01 and 2010/11 activity rose by 5.3% a year, quality of care improved, and life expectancy grew by nearly 3 months a year for women and almost 4 months a year for men. As funding slowed after 2010 so too did activity. Between 2010/11 and 2017/18 activity grew by 3.6% a year, quality gains slowed and life expectancy has stalled overall and for some groups declined (notably for women younger than 50 in deprived areas). But it is not just life expectancy that has changed. Over the past two decades the amount of life spent living with long-term health conditions has increased and more people are living for prolonged periods with multiple long-term health problems. New technologies, changes in prices, and the increasing availability of information about treatments have increased clinician and public expectations about what the NHS can and should provide. Medical advances have meant more treatments can be provid...