Which factor was a primary reason for the shift described in this excerpt? * Historically, one of the most significant migrations of population
in the United States has been the movement of people from rural
to urban areas. To appreciate the magnitude of this shift,
consider the fact that in 1800, 94% of the U. S. population lived in
a rural area, compared with 60% in 1890 and only 25% in 1990!
-Stephan J. Goetz, Migration and Local Labor Markets, 1999
a. Kinship networks
b. Economic transformation
c. Government reform
d. Climate change