Total retail sales in the U.S. topped $4.53 trillion in 2013, and ecommerce accounted for a significant portion of that growth, up 16.9% in 2013 — or nearly $40 billion — of the more than $4.53 trillion, according to a new report from eMarketer. The report estimates U.S. retail ecommerce sales will increase 15.5% in 2014 to reach $304.1 billion, up from $263.3 billion in 2013. That growth will represent more than 20% of this year’s $199.4 billion increase in total retail sales.