Midia Research founder Mark Mulligan, who’s spent more than a decade scrutinizing the digital-music market, predicts the music download business will stutter at around $600 million in 2019—a depressing fall from $3.9 billion in 2012, when Apple’s iTunes Store (the world’s preeminent downloads platform) was at its revenue peak. In 2015, downloads declined by 16%, and they look to slide as much as 30% more this year.