Steven E. Robbins, Adel M. Hanna, and Gerard J. Gouw. "Overload protection: avoidance response to heavy plantar surface loading," Medicine and Science in Sports and Exercise, 20(1), 1988, pp. 85-92.
...the paradoxical low incidence of similar injuries reported in barefoot populations implies that modern footwear may produce injuries that normally would not be present without their use.......sensory-induced behavior associated with the physical inter-action of the plantar surface with the ground (in the unshod), or the footwear and underlying surface (in the shod), is considered unimportant to the traditional thesis. This omission is astonishing because logically, the plantar surface, being a highly sensible layer, would produce significant sensations in either state, and it is common knowledge that noxious plantar skin sensation can easily induce avoidance behavior......Many years have passed since the first of a series of reports consistently indicated that there is no correlation between the amount of shoe cushioning and impact absorption of footwear during locomotion. Similarly, epidemiological studies over the same period have provided no evidence of a trend of enhanced protection with modern athletic footwear. Rather than being dismissed as glaringly incomplete and inadequate, these concepts are still being promoted by biomechanists, physicians, and manufacturers of footwear as an effective solution to the injury problem in high impact environments.
There can also be other explanations of this current situation. Investors may have become too preoccupied with sophisticated hardware rather than their principal task of performing experiments which test hypotheses. Further, as much of this research is "in-house" (performed by footwear company staff or as direct contracts from footwear manufacturers), intellectual freedom may be compromised, resulting in a reluctance on the part of investors to draw conclusions that may undermine current product lines promoted by their employers or patrons.
Whatever the cause, there has been little effort directed at explaining reported data and searching for alternative explanations. Rather, invalid models have lead to footwear that do not protect and in fact may be injurious.