Interactions as a share of impressions fell to 2.08% in 2017, down from 2.69% in 2016. The US interaction rate has held reasonably steady since 2011, dropping below 2% only once (1.59% in 2014) and rising above 3% also once (3.03% in 2013). Though the 2017 figure represents on 0.61 percentage point (pp) fall on the previous year, it is only 0.35pp below the seven-year average of 2.43%.
By contrast, click-through rates have been declining steaily since 2013, when overall CTR peaked at 0.16%. In 2017, this figure had fallen to 0.08%, with rich media on 0.08% and standard media...