Public goods are traditionally defined by two key characteristics: non-excludability and non-rivalry. A good is non-excludable when it is either impossible or highly inefficient to prevent individuals from accessing it, regardless of whether they have paid for it. A good is non-rivalrous when one person’s consumption does not reduce its availability to others (Samuelson 1954; Kaul and Mendoza 2003; Reiss 2021). These features distinguish public goods from private goods, which are both excludable and rivalrous.