What did Wilbur Zelinsky's model of migration predict?

Wilbur Zelinsky's most previous job was a geography professor at Pennsylvania State University. Zelinsky's model proved five different phases for different types of society, shown here: (1) Premodern traditional society: very little migration (2) Early transitional society: high rate of migration from rural areas to cities (3) Late transitional society: urban to urban migration (4) Advanced society: urban to suburban migration (5) Future super advanced society: interurban migration.