U.S. e-commerce increased 11% last year to surpass $155 billion in sales, according to Forrester Research. The company is forecasting 11% growth this year as well. The research and forecast show that e-commerce growth is starting to cool, although online sales growth is outpacing that of total retail. "There are still high levels of growth. But we are on a much bigger base now," said Sucharita Mulpuru, e-commerce analyst at Forrester.