Where Pi has a lower value after transfer of prestress. The small reduction in the value of Pj to Pi occurs because the force in the prestressing steel immediately after transfer is less than the initial jacking prestress force Pj. However, since it is difficult to accurately determine the reduced value of Pi ,and since observations indicate that the reduction is only a few percentage points, it is possible to use the initial value of Pi before transfer in Equations 3.2 through 3.4, or reduce it by about 10 percent for refinement if desired.