Although users are spending more time with Facebook-owned Instagram, it didn't make up for the decline in usage of Facebook's primary service. The Nielsen data wasn't the only bad news for Facebook. A new study of teens by Common Sense Media cited by Axios found that only 15% of those aged 13 to 17 said their "go-to social site" was Facebook. In 2012, it was the go-to site for 68% of that age group. The Nielsen data offered an additional worrisome detail for Facebook. Over the last two years, its share of digital content consumption across all its apps has dwindled from just under 20% to around 15%. By contrast, archrival Google, buoyed by YouTube, has grown markedly - from less than 25% two year ago to almost 35% today. Get the full story at Business Insider