WASHINGTON (MarketWatch) - The U.S. economy grew by a 4% annual pace in the second quarter, bouncing back from a revised 2.1% decline in the first three months of the year, according to a preliminary government estimate. Economists polled by MarketWatch predicted GDP would grow by a seasonally adjusted 3.2%. Consumer spending, the main source of economic activity, accelerated to show a solid 2.5% gain after a meager 1.2% rise in the first quarter. Bigger stock dividends helped to boost inflation-adjusted disposable income by 3.8% and underpin the upturn in spending, mainly on durable goods such as cars and trucks. Also adding to U.S. growth was a pickup in construction spending, increased business investment, a bigger buildup in inventories and slightly higher government spending, the Commerce Department said Wednesday. The increase in inventories was valued at $93.4 billion vs. a $35.2 billion increase in the first quarter. The only significant drag on second-quarter growth was net exports. Imports rose a faster 11.7% compared to a 9.5% advance in exports.