Fermi Estimation

Fermi problems ask you to estimate quantities with limited information. "How many piano tuners are in Chicago?" Break it down: Chicago population ($3$ million), households ($1$ million), pianos per household ($1$ in $20$), tunings per year ($1$), time per tuning ($2$ hours), tuner capacity ($1000$ tunings/year).

Result: about $50$ tuners. Show your reasoning. Round liberally. The process matters more than precision.