Wage and salary indices describe the monthly development of the wages and salaries sum in different industries. Sums of wages and salaries refer to the gross totals of wages and salaries enterprises have paid. Wage and salary indices exclude incentive stock options but include bonuses and other one-off reward items. The calculation is based on estimation of change. Sums by industry are calculated from information on the enterprises with comparable data on wages and salaries from both the examined month and the corresponding month of the previous year. These sums are used to calculate annual changes by industry. Calculation of the annual changes also takes into consideration enterprise openings and closures, as well as restructuring and change of activity. The annual changes thus obtained are used to raise the wage and salary index of the corresponding month of the previous year. The latest index figures may become slightly revised as the volume of data grows and enterprises report changes to their data. Due to supplementations the data will become updated in releases for over twelve months.