A year after Facebook Inc's fumbled IPO, Wall Street remains slow to recognize what Chief Operating Officer Sheryl Sandberg argues has been an across-the-board improvement in its business. Facebook's ability to deliver ads to mobile phones, improvements in measuring the effectiveness of its ads and increasing user engagement have all put the world's largest social network in a better position than before the IPO, Sandberg told the Reuters Global Technology Summit on Wednesday. "When I look back at the last year since we went public, I believe we are unequivocally a much stronger company today than we were on literally any metric I can think of," Sandberg said at the Reuters Global Technology Summit on Wednesday. Facebook became the first U.S. technology company to debut with a value of more than $100 billion, in May 2012. Its shares have lost almost 40 percent of their value since. "I can't speak to the stock price but I do feel strongly that we ar