Indexes of aggregate weekly hours are calculated by dividing the current month's aggregate hours by the average of the 12 monthly figures, for the base year. For basic industries, the hours aggregates are the product of average weekly hours and employment of workers to which the hours apply (all employees or production and nonsupervisory employees). At all higher levels of industry aggregation, hours aggregates are the sum of the component aggregates.
The series comes from the 'Current Employment Statistics (Establishment Survey)'
The source code is: CES4000000016
Source: US. Bureau of Labor Statistics
Release: Employment Situation
US. Bureau of Labor Statistics, Indexes of Aggregate Weekly Hours of All Employees: Trade, Transportation, and Utilities [CES4000000016], retrieved from FRED, Federal Reserve Bank of St. Louis https://research.stlouisfed.org/fred2/series/CES4000000016/, October 4, 2015.