Complex sentence: Through a dissection of the theory of product life-cycle and its suggestion of urban decline from disinvestment of outdated industry, Friedrichs attributes the root cause of shrinking cities as the lack of industrial diversification within specific urban areas.
Split into simpler sentences: Through a dissection of the theory of product-cycle induced urban decline, Friedrichs explains the phenomenon of urban disinvestment. He furthers his explanation by highlighting the root cause of disinvestment as resulting from at lack of industrial diversification within specific urban areas.