The United Nations predicts human population growth will surpass 9 billion around 2050. We know the consequences of overpopulation have the potential to be catastrophic in terms of our continued existence on the planet, with negative environmental effects already visible. Limiting the number of children we have seems like one obvious way to tackle the problem. But is there a moral imperative to limit reproduction? Is having multiple children a right, and if so is it one we should give up for the greater good? What can we do ethically about controlling population? John and Ken have more than a word with Sarah Conly from Bowdoin College, author of One Child: Do We Have a Right to More?