FactSet Senior Earnings Analyst John Butters provides an update of the key metrics for the third quarter earnings season for the S&P 500 as we're in the middle of the peak weeks of the earnings season. He then discusses revisions to earnings estimates for S&P 500 companies for the fourth quarter. Analysts have been increasing earnings estimates for S&P 500 companies over the past few quarters--is this trend continuing in the fourth quarter?