Apple Inc (AAPL.O) became the first U.S. company to top the $800 billion mark in market capitalization on Tuesday, slightly more than two years after it crossed the $700 billion threshold.
The iPhone maker's shares have gained 33 percent this year and almost 50 percent since the U.S. election in November. The company represents about 4 percent of the $21.7 trillion that makes up the entire S&P 500 .SPX index.
Apple accounted for as much as 4.9 percent of the S&P 500 in September 2012 but is a smaller percentage now as the index as a whole has rallied more than 7 percent this year.