ByJohn S. McClenahen The Conference Board's April index of leading economic indicators, due for release on May 20, is likely to signal a slower-paced recovery. Merrill Lynch & Co., for example, is expecting the index to show "only" a 0.2% rise. UBS Investment Research is even more cautious, anticipating just a 0.1% increase. The index generally previews the U.S. economy's performance three to six months ahead, and Merrill notes it has been decelerating since last October, "suggesting that growth in the second half of [this] year could decelerate faster than investors are currently expecting." The Conference Board is a New York-based business research group.