As the 2015 deadline for the attainment of the millennium development goals (MDGs) approaches, a UN working group has released a draft proposal for their successors. Among the health related targets of the proposed new sustainable development goals (SDGs) are:

• Reduce maternal mortality to less than 70 per 100 000 live births by 2030
• End preventable deaths of newborns and under 5s by 2030
• End the epidemics of AIDS, tuberculosis, malaria, and neglected tropical diseases by 2030
• Reduce premature mortality from non-communicable diseases (NCDs) by one third by 2030
• Halve deaths and injuries from road traffic accidents by 2020
• Achieve universal health coverage for all

While these targets are all undeniably important, health budgets in low and middle income countries remain limited and the growth of global health aid has slowed dramatically in recent years. Policymakers have to make some hard decisions about what and who to prioritise. As long as scarcity remains a (political) fact, tradeoffs between worthy health targets remain inevitable, and increased funding for one cause entails decreased funding for another. The SDG proposal thus raises an important question: how should the international development community balance further progress towards the original MDGs—with their emphasis on child mortality, maternal health, and communicable diseases—versus stemming the growing burden of NCDs?

It is generally agreed that NCDs, now the leading killers in most parts of the world, deserve higher priority, and that tackling their growing burden is extremely important. In a recent paper in the American Journal of Tropical Medicine and Hygiene, we argue that this near consensus opinion is false, or at least often vastly overstated. Our argument turns on two simple premises, which together have an important consequence.

Firstly, while cost and benefit matter, it also matters how benefits are distributed. In particular, those who are least advantaged—the worst off—deserve highest priority. A wide body of research shows that people regard health improvements of the same size as much more valuable when they are experienced by people who are worse off. Moreover, the idea that the worst off deserve priority is widely endorsed in political philosophy and medical ethics.

Secondly, the worst off people are those with the worst overall lives, rather than those who are currently experiencing the most severe health problems. Dying prematurely and experiencing deprivation over the course of their lives both make people worse off. Concern for a person’s whole lifetime explains why the international community has and should care about those who die very young.

Looking at a person’s whole life implies that those who die young are always among the global worst off. Compare someone who dies at age 5 with someone who dies at age 50. Could the 50 year old be worse off even though he lived 10 times longer? In order for that to be so, each of the 5 year old’s brief years would have to have been 10 times better than each of the years of the 50 year old. Even for people who spend their lives with chronic conditions, this almost never happens. Virtually no one who lives to age 50 will have had a worse overall life than someone who dies at age 5. Even those who die as adolescents and young adults are very likely to be much worse off than those who die in their 50s and older.

Giving priority to the worst off therefore implies that children, adolescents, and adults who die young deserve the highest priority for limited health resources. But young people in the developing world die primarily of communicable diseases, birth related complications, and nutritional disorders. In contrast, NCDs primarily affect older adults.

Making continued progress in these areas would also confer huge benefits for relatively miniscule costs. According to a recent Lancet Commission report, a massive health system scale-up towards a “grand convergence” on maternal and child health, which would prevent 5-8 million deaths in LMICs by 2035, would have an incremental cost of just $38 billion per year in 2016-2025. The benefits, which would accrue to the very worst off, would exceed costs by a factor of about 20.

For the most part, interventions to prevent and treat child mortality, communicable diseases, and maternal mortality are cheap, highly effective, and help the globally worst off. They ought to remain “at the heart of global health and development goals.”

So, what does the principle of priority to the worst off imply about how to pursue the other SDGs?

Firstly, campaigns to reduce the burden of NCDs ought to focus on the burden of NCDs among young adults and the very poor. One helpful proposal in this direction is “80 x 20 x 40”—that is, to reduce premature mortality from all NCDs by 80% in individuals younger than 40 years by the year 2020.

Secondly, in pursuing universal healthcare, governments should begin by expanding coverage for cost effective services for the worst off patients. Moreover, they should place comparatively greater emphasis on providing coverage for the worst off than they should on providing financial risk protection for the comparatively better off (see here for further discussion).

Finally, donors and national governments should also assign high priority to other development goals which benefit the worst off. One important example is road traffic accidents, where the mortality burden is borne disproportionately by young adults. Road injuries are the leading cause of death among males aged 5 to 29; they are fourth among women aged 15-29.

The compilation of the SDGs is a remarkable achievement. But pursuing ambitious development goals requires making tough decisions about priorities. In pursuing these goals, policymakers must not give short shrift to the most disadvantaged; after all, it is they who have the weightiest claims on the benefits of development.

Daniel Sharp is a former fellow at the Clinical Center Department of Bioethics, National Institutes of Health. He is currently a Fulbright scholar at the Vienna University of Business and Economics.

Joseph Millum is a bioethicist at the Clinical Center Department of Bioethics and Fogarty International Center, National Institutes of Health.

The authors have read and understood BMJ policy on declaration of interests and declare the following interests: None. The views expressed are the authors’ own. They do not represent the position or policy of the National Institutes of Health, US Public Health Service, or the Department of Health and Human Services.