The mass shootings in Boulder and Atlanta have reignited the debate about gun violence and gun policy. President Biden is calling for a ban on assault weapons with high-capacity magazines. He's also taking executive action. Last year broke records for both gun sales and gun deaths in the U.S. as people bought at least 20 million guns. Still, the data and research that could inform policy are lacking, which we explore with Dan Gorenstein, host of the new health policy podcast, "Tradeoffs."