More U.S. companies are exceeding sales forecasts than any time in four years, helping extend the biggest stock-market rally since 1936.

Caterpillar Inc. and United Parcel Service Inc., barometers for the economy because of their building and delivery businesses are among the 71% of Standard & Poor’s 500 Index companies that reported more revenue last quarter than analysts estimated, the largest proportion since at least 2006, according to data compiled by Bloomberg. Sales beat projections by an average 2.2 percent, the most in two years, the data show.

According to the news service, while U.S. earnings have surpassed Wall Street estimates for seven straight quarters, sales have trailed forecasts on average since 2008, as the U.S. ended its worst recession in seven decades and employers cut as many as 8.75 million workers. Bank of America Corp. and Penn Capital Management say unexpected revenue growth shows the economy is expanding enough that companies can stop firing people and closing plants.

“You really did need top-line growth because the cost- cutting got to where you couldn’t cut anymore,” Eric Green, a money manager at Penn Capital Management in Philadelphia, told Bloomberg. “But you’re seeing it now. Many companies are having that nice top-line growth, and as that goes up, it should have a magnified effect on earnings. It’s very positive for the equity markets.”

Bloomberg notes strengthening global economic growth and higher-than-estimated earnings have pushed the S&P 500 up 29% since July 2, its 2010 low. The index topped 1,300 on Feb. 1, a 31-month high, after reports showed U.S. manufacturing accelerated at the fastest pace since May 2004 last month and consumer spending exceeded forecasts.