Alibaba Group Holding Ltd. is knocking Amazon.com Inc. off its perch as the world’s largest online retailer by market capitalization, signaling the ascendance of a global rival for investor and consumer dollars. Alibaba begins trading on the New York Stock Exchange today after pricing its initial public offering yesterday at $68 a share, putting the Hangzhou, China-based company’s valuation at $167.6 billion. That exceeds Amazon’s market capitalization of $150.2 billion, as of its closing price in New York yesterday of $325. http://www.bloomberg.com/news/2014-09-18/alibaba-o...