Last year, online retail sales in seven out of 15 product categories accounted for 5 percent or more of the $2.07 trillion in total retail spending. And this year, that figure is expected to increase to 9 categories out of 15, Silverman said. It is estimated that retail sales this year could reach $2.13 trillion. In the computer hardware and software category, 34 percent is expected to come from online transactions. Sales of all online tickets, including travel, events and movies, are expected to capture 20 percent of all ticket sales, while 15 percent of all book sales are anticipated to be online, according to the study.