LIKE chickens, people have a pecking order. Sir Michael Marmot shows that this order is strongly related to health and longevity. The higher in the order, the longer and healthier the life. On average, Oscar winners live about four years more than other Hollywood actors, and at either end of a 12-mile subway ride between poor downtown Washington, DC, and rich white Montgomery County there is a difference in life expectancy of 20 years.

The roots of Sir Michael's book lie in his work studying the health of Britain's civil servants in the 1970s. He was surprised to find that bureaucrats in the lower grades had a greater risk of heart disease than those higher up the ladder. Sir Michael, who is a professor of epidemiology and public health at University College London, has spent three decades looking at this pattern and picking apart issues of causality—for example, do civil servants get to the top of the tree because they are healthier to start with (or have better genes)? Or is it getting to the top that makes them healthier? Such issues are dealt with (rather exhaustively) in this book.

Others have found similar relationships between health and status in countries all around the world—including relatively classless places such as Sweden. The phenomenon, it seems, is mostly due to stress. Long-term stress damages health, and ultimately shortens lifespans. Studies on primates, including Whitehall civil servants, show that lower-status workers have higher levels of the stress hormones that organise the body's response to threat.

The book argues that human hierarchies cannot be eliminated. But since their consequences for health vary vastly from place to place, the differences between those at the top and the bottom can be made smaller. It is possible to reduce the disparity in the lifespan of a boss and his workers. But how? Sir Michael suggests giving people greater autonomy and social cohesion rather than raising their pay or improving their access to medical services. In concrete terms, that might translate into fewer working hours or more flexible working. Those looking for a quick fix, however, will be sorry to find that job-title inflation—from, say, secretary to personal assistant—is unlikely to help.