Definition:
There is a quotient, given in percent, of the difference between the value of the accounting unit on the last working Day of the last month of a given quarter and the value of the accounting unit as established on that last working Day of a month which occur 36 months earlier, and the Said value of the accounting unit on the last working Day of the month which occur 36 months earlier. That open fund which has taken in contributions for no less than 24 months shall at the end of the last month of each quarter establish its rate of return for the past 36 months. The rate of return shall be reported to the supervisory body and to one of those news agencies which the supervisory body has designated.

Source:

• Act of 28 August 1997 on the Organisation and Operation of Pension Funds
  Place of publication: (Dz. U. z 2023 r. poz. 930, z późn. zm.)