In Taylor v. Workers' Comp. Appeals Bd. (1979) 95 Cal.App.3d 139 the injured worker sustained three successive industrial back injuries. One occurred in January 1972 and the two others occurred after April 1, 1972. All three injuries became permanent and stationary on April 16, 1976. As a result of the three injuries the worker sustained 69 percent permanent disability. The court observed as the three injuries became permanent and stationary at the same time "that no permanent disability caused by any of them is 'previous' or 'prior' to another within the meaning of section 4750, that an apportionment among them is accordingly not required by that section, and that none can be made unless there is 'substantial evidence' that the 'normal progression' of the first injury would have caused permanent disability." ( Taylor, supra, 95 Cal.App.3d at pp. 146-147.) The court found no substantial evidence supporting any apportionment between the three injuries. The court then held the injured was entitled to a 69 percent permanent disability award calculated upon the benefit rate applicable at the time the last injury giving rise to such benefits occurred. ( Taylor, supra, at p. 149.)