There is a relation between the size of an asteroid and the frequency of them entering Earth's atmosphere.
Diameters of 5 to 10 m (16 to 33 ft) approximately once a year.Diameters around 50 m (164 ft) approximately once every 1,000 yearsDiameters of about 1 km (0.62 mi) approximately every 500,000 years.Diameters > 5 km (3 mi) approximately once every ten million years