Complex sentence: This decline in population over the past century reflects the national trends as shown the same respective census reports of declines in family sizes and the shift of the population to a more urbanized society with its concomitant economic offerings and social advantages.
Split into simpler sentences: This decline in population over the past century reflects the national trends as shown by the same respective census. These reports trflrct declines in family sizes and the shift of the population to a more urbanized society with its concomitant economic offerings and social advantages.