The S&P 500 and index-related exchange traded funds have been making new highs as U.S. companies are on track to report year-over-year growth in revenues for the first time since 2014.

Year-to-date, the SPDR S&P 500 ETF (NYSEArca: SPY), iShares Core S&P 500 ETF (NYSEArca: IVV) and Vanguard 500 Index (NYSEArca: VOO) gained 7.6% as the S&P 500 Index hit a new intra-day high.

Fueling the renewed market rally, U.S. companies are reporting increased revenue growth. For the week ended July 25, the blended revenue growth rate for the S&P 500 rose to 0.1%, above the year-over-year decline of -0.3%at the end of the previous week and the year-over-year fall of -0.8% at the end of the second quarter, writes John Butters, Senior Earnings Analyst, for FactSet.

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The index is also set to report growth in revenues for the quarter, potentially marking the first time the S&P 500 will see see year-over-year growth in sales since the fourth quarter of 2014.

“Two factors typically drive the improvement in the revenue growth rate during an average earnings season: the number (or percentage) of companies that report revenues above estimates and the aggregate amount by which companies report revenues above (or below) estimates,” Butters said.

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So far, 57% of companies that reported revenues above estimates was slightly above the five-year average of 55%. Additionally, the aggregate reported revenue estimates for Q2 at 1.2% is twice as large as the five-year average of 0.6%.

“So, while both numbers are above average, the surprise percentage for Q2 is the main driver of the increase in the Q2 revenue growth rate since June 30,” Butters said.