Quality of life has many dimensions, from the air residents breathe to how safe they feel walking the streets. The latest report from the McKinsey Global Institute (MGI), Smart cities: Digital solutions for a more livable future, analyzes how dozens of digital applications address these kinds of practical and very human concerns. It finds that cities can use smart technologies to improve some key quality-of-life indicators by 10 to 30 percent—numbers that translate into lives saved, fewer crime incidents, shorter commutes, a reduced health burden, and carbon emissions averted.