News Release

25 years of global progress across sanitation service levels assessed against Millennium Development Goal

Novel metric evaluating safe management of human waste could help inform continued progress

Peer-Reviewed Publication


Overall global Ladder Score (left) and Millennium Development Goal (MDG) Percentage Improved (right) for 1990 and 2015.

image: Overall global Ladder Score (left) and Millennium Development Goal (MDG) Percentage Improved (right) for 1990 and 2015. view more 

Credit: Zimmerman et al., 2022, PLOS Water, CC-BY 4.0 (

A new analysis is the first to apply a novel metric for evaluating improvements in sanitation across individual countries between 1990 and 2015, surfacing insights that could inform further progress. Julia Zimmerman of the University of Alabama, Tuscaloosa, and U.S. Army Engineer Research and Development Center, Mississippi and colleagues present these findings in the open-access journal PLOS Water on February 15, 2022.

In 2004, United Nations Member States pledged to take actions that, by 2015, would reduce the proportion of people lacking access to basic sanitation by 50 percent compared to 1990 levels. While progress occurred, it fell short of this Millennium Development Goal. However, concerns arose that the simple pass-fail metric used to track progress might miss meaningful gains, such as a household switching from open defecation to a shared latrine. Or, it could limit progress by incentivizing only the easiest improvements. Instead, a ladder-based metric that could capture incremental progress was developed, but had not yet been applied to the Millennium Development Goal period.

Now, Zimmerman and colleagues have revisited data from 1990 to 2015 and applied the new Sanitation Ladder Score to 190 countries, accounting for 99.8 percent of the global population. They found that most countries showed a greater degree of progress with the ladder score than with the previous pass-fail metric. Forty-one countries jumped to a higher level of progress on the ladder score than on the pass-fail metric, and five fell to a lower level (Libya, Seychelles, Granada, Aruba, and French Polynesia).

To highlight possibilities for improvement from a variety of starting points, the researchers discussed in greater detail data from six countries with notable progress on the ladder metric: Ghana, Ethiopia, Cambodia, Lao People’s Democratic Republic, Nepal, and Poland.

The researchers suggest that the novel insights provided by the ladder score for 1990 to 2015 could help inform efforts in countries currently looking to improve sanitation access under the United Nations’ Sustainable Development Goals for 2030.

The authors add: “Retrospective analysis of progress across sanitation service levels during the MDG period can illuminate the many different approaches used to address urban and rural sanitation deficits and provide insight into how to improve household sanitation access in diverse settings.”

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