In Episode 3 of the Covid-19 Dispatch series, we talk to The Atlantic’s Derek Thompson, who recently wrote about contact tracing. In the fight against Covid-19, this critical public health tool has been used unevenly. Thompson notes that South Korea and Singapore have had success with smartphone apps, but that South Korea’s reliance on GPS, along with surveillance video and credit card transactions, raised privacy concerns and may have discouraged participation. Singapore used Bluetooth proximity data, which doesn’t reveal geolocation information. The latter may provide the model for tracing efforts in the US and elsewhere.