WASHINGTON — U.S. businesses posted the most job openings on record in April for the second straight month, underscoring the economy’s strong demand for workers.The number of available jobs rose 1 percent to 6.7 million from 6.6 million in March, the Labor Department said Tuesday. That’s the most since records began in December 2000.Steady economic growth has encouraged employers to step up hiring. That pushed the unemployment rate in May to an 18-year low of 3.8 percent. Faster consumer spending is expected to lift economic growth above a 3 percent annual pace in the April-June quarter, after growth lagged a bit in the first three months of the year.There are now more open jobs than there are unemployed people, a historically unusual development that should give workers more leverage to demand raises. At the peak of the recession, there were, on average, 6.7 unemployed people for each job. Now, that figure has fallen to just 0.95 per opening.Yet wage gains remain sluggish, compared to previous periods when the unemployment rate was this low. Hourly pay rose 2.8 percent in May for all workers, excluding managers, compared with a year earlier. In April 2000, the last time the unemployment rate was at 3.8 percent, hourly pay was up nearly 4 percent.