Online retail sales were up 12.1% on average year-on-year (YoY) in 2017, according to the latest figures from the IMRG Capgemini e-Retail Sales Index. Compared to 2016’s YoY average of 15.9%,  the fall in annual growth is one of multiple indicators of a maturing market. Indeed, across the twelve months of 2017 only March and April showed…