Source: Millennial migration a boon for AZ cities, loss for rural areas | Arizona | by Preston Scott-Hall Taryn Martin, 21, grew up in Vail, a small town in Pima County with approximately 10,000 residents. Her family’s land stretched across the countryside. She rode horses during the day and enjoyed starry skies at night.   But at 18, Martin decided to leave her home and move to Phoenix, one of