a well-designed market increases the safety of the market via transparency, quality, or insurance, thereby enabling good interactions to occur. It provides thickness, which enables participants from different sides of a multisided market to find one another more easily. It minimizes congestion, which hampers successful searches when too many people participate or low quality drives out high. And it minimizes repugnant activity—which explains why platform designers forbid porn on iTunes, human organ sales on Alibaba, and child labor on Upwork.
