When first interviewing at Point Nine, I was asked to define marketplace liquidity. At the time, I had a vague understanding of liquidity and luckily gave a good enough answer to make it through the interviews. That being said, I had never given much thought to how exactly you go about understanding its key drivers and measuring it. Over a year later, having spoken to hundreds of different marketplaces, I’m finally getting to the bottom of WTF marketplace liquidity is all about.