ChannelAdvisor, a company that provides companies guidance on how to sell more products through third-party shopping sites, stated today that “client sales growth” on Amazon and eBay has declined from November to December. According to the company, merchants’ sales on Amazon dropped from 43.7 percent growth in November to 29.8 percent in December. While sellers on eBay saw sales growth drop from 27.4 in November to 22.2. percent in December. [Source: Reuters]