Most people in the developed world don’t have to worry about losing the right to live where they do. If you have a deed or a rental contract, it is unlikely that someone will turn up tomorrow with their own paperwork and kick you out. That security means owners who build a new kitchen know they can enjoy it for decades or increase the value of their property when they sell. Farmers can plant trees that take years to mature, knowing they won’t be kicked off the land by the time they bear fruit.

Imagine if you weren’t sure if you really owned your house. Perhaps you could keep living here next year. Maybe someone would boot you out. Not only would you be psychologically worse off, but you would also be much less likely to invest in making your home or land better.

Yet, for most people in developing countries, secure property rights are a rare luxury. Globally, 70 percent of the world’s population cannot access formal land registration systems. One in five, or almost 1 billion people, consider it likely or very likely they will be evicted in the next five years.

Getting more land security is one of the many goals world leaders signed up to achieve by 2030 when they set the Sustainable Development Goals (SDGs) in 2015. This year is halftime for those global goals, but we are still far from halfway to completion. Indeed, despite many development organizations focusing on achieving better land tenure, progress has been negligible, with zero countries reporting any progress.

The Copenhagen Consensus think tank has worked with some of the world’s best economists to identify the most effective ways to speed the delivery of the SDGs. In a just-published research paper, the former lead land specialist at the World Bank, Frank Byamugisha, and his colleagues show developing better land registration systems would deliver amazing benefits.

The researchers focused on Sub-Saharan Africa because it has the lowest proportion of land officially mapped and categorized by governments. At just 14 percent, Sub-Saharan Africa has the weakest land property rights and the highest levels of disputes. The continent also has by far the most adults insecure in property tenure, along with the highest cost of registering land worldwide.

Path-breaking countries like Rwanda have shown how it is possible to register land, digitize the information, and provide legal mediation to resolve inevitable land disputes.

Nonetheless, achieving greater rural land security in Africa will take enormous effort because 86 percent of all the continent’s rural land plots are still unregistered. The total cost for the continent will run to $21.7 billion.

However, the benefits would be much larger. When farmers know they own their land, they are more willing to make expensive investments to increase long-term productivity. They can also use their land deed as collateral to borrow money for investments like farm equipment or property expansion.

Unfortunately, there is relatively little direct evidence from Africa on what the effect will be on productivity. That means researchers have to use evidence from the rest of the world, which leaves the effect less certain. Nonetheless, the evidence suggests the benefits from more land security through higher agricultural productivity would likely increase household incomes by almost $400 billion.

Spending $21.7 billion to deliver almost $400 billion in benefits is a good investment, achieving $18 of social benefits for each dollar spent.

The case for increasing land tenure security is even stronger for the almost half a billion people living in Sub-Saharan Africa’s urban areas. More than one-third of all urban land parcels are unregistered, and it would cost a much smaller $5.2 billion to survey and register this land, including the land in slums, along with setting up dispute resolution and running the system.

Moreover, the benefits of tenure in urban areas are better documented. Homes with secure registration are, on average, worth 25 percent more. This is not surprising. A house is worth more simply because the owner has the financial and psychological security of knowing they own it. The researchers show the benefits of providing more secure urban tenure are about $160 billion, or 30 times the cost.

Currently, the world needs to deliver on many of the most important promises of the SDGs, partly because this agenda set out to do everything at once.

Instead, we need to prioritize the best solutions first. Being wildly off-track on our global promises can seem unsettling, but it can also be an energizing wake-up moment. We urgently need to focus on investing in the very best solutions.

Improving urban tenure security, which at low costs would make hundreds of millions of people better off, is one such investment. Rarely is the world offered an opportunity that delivers up to $30 of social benefits for each dollar invested. We should take it!