The economy slowed, but indexes climbed for a second day in a row on Wednesday. The gains were decisive. All 10 sectors in the S&P 500 gained. The government said the economy grew at an annual rate of 1.8 percent in the first quarter, down significantly from an earlier estimate of 2.4 percent. It might seem a little odd for stocks and growth to go in opposite directions, but analysts said it made sense. The slower growth made investors less anxious that the Fed might act too soon to end stimulus measures. Investors also realized they dumped too many stocks last week, when they panicked after the Fed said how it might end the measures.