What is the test for deducting a contingency from a claim for loss of income due to a motor vehicle accident?

In Lewis v. Todd et al, 1980 CanLII 20 (SCC), [1980] 2 S.C.R. 694; 34 N.R. 1; 115 D.L.R.(3d) 257; 14 C.C.L.T. 294, Dickson, J., observed at p. 714 [S.C.R.], the following: "In principle, there is no reason why a court should not recognize, and give effect to, those contingencies, good or bad, which may reasonably be foreseen. This is not to say that the courts are justified in imposing an automatic contingency deduction. Not all contingencies are adverse. The court must attempt to evaluate the probability of the occurrence of the stated contingency,,,” Reference is also made to actuarial evidence being of aid when contingencies are under consideration. In the circumstances of this case such evidence is nonexistent.