"Six months ago, the economy was in a nose dive, people were talking about the possibility of another depression, the statistics all suggested a vertical decline. None of that is the situation right now," Summers said Sunday.
On Monday, the Institute of Supply Management said contraction in the manufacturing sector had slowed. The Commerce Department reported a 0.3 percent increase in construction spending in June.
By close, the Dow Jones industrial average gained 114.95 points, 1.25 percent, to 9,286.56. The S&P 500 index gained 15.16 points, 1.53 percent, to 1,002.63. The Nasdaq index added 30.11 points, 1.52 percent, to 2,008.61.
On the New York Stock Exchange, 2,542 stocks advanced and 522 declined on a volume of 5.6 billion shares traded.
The benchmark 10-year Treasury fell 1 7/32 to yield 3.631 percent.
The euro rose to $1.4412, compared with Friday's 1.4253. Against the yen, the dollar rose to 95.25 yen, compared with Friday's 94.62 yen.
In Japan, the Nikkei 225 index lost 0.04 percent, 4.36 points, to 10,352.47.
In Britain, the FTSE 100 index added 74.10 points, 1.61 percent, to 4,682.46.