Why do online marketing companies advertise on sites like Craigslist?

In the first quarter of 2017, online marketers spent $2.4 billion on advertising, according to market research firm Market Data Solutions.This includes $1.5 billion on paid ads and $800 million on sponsored content.According to research firm eMarketer, advertising spending in the U.S. reached a record $19.5 trillion in the first six months of 2017.While that may seem like a lot of money, a closer ...