In this Q4 update to the online retail sales forecast for the US, Forrester has increased its online sales penetration projections for 2020 by half a percentage point based on sales data. Despite softer overall retail sales in 2015, online retailing illustrates its resilience and strong year-over-year growth. The fastest online growth will come from the pet supplies and small appliances categories. The most popular categories bought online will continue to be consumer electronics and clothing. The forecast details growth across 31 product categories with historical data going back to 1998, and it calculates the share of online retail sales for each product category.