Social-media platforms used to get most of their content for free. That dynamic is changing…Though there is more content than ever, platforms are competing harder than ever to get it. “There’s an arms race to acquire creators,” says Li Jin, founder of Atelier Ventures, a venture-capital firm. Startups are developing new ways for creators to monetise their work. Substack gives writers 90% of the subscription fees they charge for newsletters; together its top ten authors earn more than $15m a year.