Since entrepreneurs tend to see the proverbial glass half full, the National Federation of Independent Businesses was justifiably concerned when its monthly index measuring optimism among small-business owners hit a 10-year low in March. Net 1% of the business owners surveyed planned to create new jobs, the lowest reading since 1990. And only net 7% expected the economy to improve by the fall. But what a difference a successful war and the spring thaw can make. In April, the index posted the largest one-month turnaround in its history -- net 36% had come to believe that the economy would get better. Yet Bill Dunkelberg, the NFIB's chief economist, cautions that the leap in entrepreneurial optimism does not suggest a return to robust growth. At most, he says, the rebound in April may indicate a return to normalcy.