Does vehicle age change how underinflated tires are?

NHTSA's 2001 measurement of 11,530 vehicles found 8% of tires on cars 3 years old or newer underinflated by 8 psi or more against 15% on cars over 6 years old, and 12% against 24% on pickups, SUVs and vans.

Share of tires deviating 8 psi or more from the maker's pressure, by vehicle age, measured in 2001. 3 years or newer, pickups and SUVs: 12%; 3 to 6 years, pickups and SUVs: 15%; Over 6 years, pickups and SUVs: 24%.

Source: NHTSA National Center for Statistics and Analysis, Tire Pressure Special Study: Vehicle Observation Data (DOT HS 809 317) · data from 2001