The deficit in the broadest measure of U.S. foreign trade narrowed sharply from April through June, despite the fact that America suffered the first deficit in 30 years in the category that includes investment income. The Commerce Department said the deficit in the current account shrank by 9.8 percent in the second quarter, falling to $33.3 billion, compared to a first quarter imbalance of $36.9 billion. It was the sharpest narrowing of the deficit since a 20.1 percent drop in the fourth quarter of 1987. The current account is the most important of all the government's trade statistics because it covers not only trade in merchandise but also trade in services, which primarily reflect the flow of investment earnings between countries.