Healthcare across the world pushes at the limits of its affordability. Driven by the development of newer and usually more expensive treatments, financial incentives that tend to reward providers for doing more, and consumerism and entitlement, and lower value care have grown alongside essential services. Market-based health systems, such as in the USA, have grown fastest while most state-funded systems have required above-inflation uplifts to keep pace with demand. The National Health System (NHS) in England has been warned that sustainability cannot be achieved through traditional methods of funding and management: services must be provided in new ways.1 Otherwise, austerity means cuts, planned or unplanned.

In this context, the notion that 20%–30% of healthcare is unnecessary and/or harmful2 offers an attractive and intuitively simple solution. Stop providing low-value care and important care will be more affordable. Picking this low-hanging fruit is simple in concept and morally defensible, but it will not be easy to achieve. It will require an unprecedented level of change.

The complexity of any large-scale change can be quantified in three dimensions:3 pervasiveness (how much of the system does it affect?), depth (how different is the new model to current ways of thinking and doing?) and size (how widely spread is the change across geographical boundaries, organisations or distinct groups of people).

The examples below illustrate that complexity in practice.

Pervasiveness can be deceptive

A study of low-value tests and surgical procedures among US Medicare patients4 identified low-value care for 42% of beneficiaries. However, this attractively large proportion accounted for just 2.7% of overall spending. Moreover, these estimates reflected ‘sensitive measures’ of overuse (ie, ones unlikely …