The article gives a definition right at the beginning: * A slave is a human being forced to work through fraud or threat of violence for no pay beyond subsiste

The article gives a definition right at the beginning: * A slave is a human being forced to work through fraud or threat of violence for no pay beyond subsistence.* What makes you think they aren't being consistent with this definition? Note that tinkering with the definition is unlikely to change the conclusion, just because human population is so much larger than it used to be. As this World Population Clock points out, estimates of the total number of humans born since 50,000 BC are around 110 billion, and 6.7 billion are alive today. Seven percent of all the humans who have ever lived are alive now: http://www.worldometers.info/population/ http://www.worldometers.info/population/ Does this make modern slavery less of a moral outrage? Not really. Those slaves really exist. You can't ameliorate the suffering of a slave just by adding more non-slaves to the population at the same time.