Europe: value of internet retail sales per online shopper 2014-2015

The source provides the followig information on the methodology:
"Data from the following sources has been used to establish these forecasts: government statistical sources and analysts, telephone interviews with 100 major retailers from all types of business (20%+ of national retail sales), and interviews with 1,000 consumers in each of the nine countries into consumer trends (9,000 in total).
The study examines the sale of merchandise to the final consumer through stores and online on a like-with-like basis. It excludes food services, the sale of automobiles, gas and fuel, tickets, holidays, insurance, and banking. This reflects ONS and OECD methodology as well as the Oxford Dictionary."