Initial claims for unemployment benefits last week dropped by a more than expected 23,000 to a preliminary reading of 340,000. The four-week moving average, a less volatile number that flattens out week-to-week fluctuations in the data, was 339,500, a decrease of 500 from the previous week, the Labor Department reported Thursday. The weekly jobless claims report is an indication of layoffs, and analysts expressed optimism that last week’s data suggests a strengthening of the labor market. .The advance number of Americans filing for continuing unemployment claims during the week ending May 11 was 2,912,000, a decrease of 112,000 from the preceding week. The four-week moving average was 2,995,250, a decrease of 23,750 from the prior week. States reported 1,776,686 persons claiming emergency unemployment compensation in the week ending May 4, a decrease of 15,415 from the prior week. There were 6,168,434 claimants in the comparable week in 2012. The total number of people claiming benefits in all programs for the week ending May 4 was 4,745,266, a decrease of 98,450 from the previous week. There were 6,168,434 claimants in the similar week last year. The largest increases in initial claims for unemployment for the week ending May 11 were in California, Florida, Georgia, Mississippi and North Carolina. The largest decreases were in Kentucky, New Jersey, New Mexico, Oregon and Tennessee.