One factor that has been blamed for the housing crisis is Airbnb. Airbnb describes itself asan online marketplace and hospitality service, enabling people to list or rent short-term lodging including vacation rentals, apartment rentals, homestays, hostel beds, or hotel rooms, with the cost of lodging set by the property owner. City councillorshave targeted these short term rentals, saying that many landlords have opted to Airbnb theirhome, rather than rent out longer term. The growth of Airbnb in Vancouver has been shown below.

Explain why a housing market at equilibrium could still have a vacancy rate of 4%.