Dear CHANCE Colleagues,

Many of us are lucky enough to live in a time and place where major human rights violations are rare and distant from our everyday lives. We see slavery as something that the history books told us ended long ago. In the United States, due to the Confiscation Acts and Emancipation Proclamation in 1863, the revolutionary war effectively ended slavery, even before ratification of the Thirteenth Amendment on December 18, 1865, formally ended “legal” slavery.

Sadly, however, slavery still exists in our world—and in larger numbers than many realize. The 2016 Global Slavery Index estimates that 45.8 million people are subject to some form of modern slavery in the world today. Slavery is not an extinct crime of the past, but a modern one.

Modern slavery is the theme of this special issue of CHANCE. Eight articles discuss challenges in measurement of slavery, methodologies for estimating its prevalence, and how to use this information to fight against the injustices of slavery. I wish to thank Dr. Davina Durgana and the Walk Free Foundation for helping to organize this special issue. Dr. Durgana, who served as a special guest editor for this issue, is a senior statistician and report co-author for the Global Slavery Index of the Walk Free Foundation, an international human rights organization with a mission to end modern slavery. The American Statistical Association named her the 2016 Statistical Advocate of the Year and Forbes included her in its Top 30 under 30 in Science in 2017 for her work on statistical modeling, human security theory, and human trafficking.

In our introduction to this issue, leading anti-trafficking scholar Dr. Kevin Bales emphasizes the importance of modern slavery prevalence estimation around the world today. Drs. Sheldon Zhang and Kyle Vincent provide strategies to estimate the global prevalence of trafficking for sexual exploitation in their article.

Then Jacqueline Joudo Larsen, senior research manager and survey methodologist of the Global Slavery Index, and Dr. Durgana describe the work of the Global Slavery Index in estimating vulnerability and measuring prevalence in 167 countries around the world. Dr. Pablo Diego-Rosell and Jacqueline Joudo Larsen provide additional information about their global household survey research program on modern slavery. Drs. Durgana and Graham Brown then explore the limitations and political concerns in global data reporting, since these data underpin many of our vulnerability and prevalence models.

Drs. Maarten Cruyff, Jan van Dijk, and Peter van der Heijden explain their impressive work using Multiple Systems Estimation (MSE) in the Netherlands to provide a robust national prevalence estimate. Dr. Durgana and Dr. Paul Zador then address the most-promising methods to estimate national prevalence in the United States of America. Finally, Fiona David, executive director of Global Research for the Global Slavery Index, concludes the issue features with a summary of the significant impact of statistics on the field of anti-modern slavery advocacy and government engagement, with a view to the future of our field.

In our columns, Howard Wainer describes in Visual Revelations how W.E.B. Du Bois told the story of slavery in the United States and people of African descent through graphics. Carl Lagoze and Lars Vilhuber then discuss how to make confidential data part of reproducible research in O Privacy, Where Art Thou?

Scott Evans