What's more, Riverside and San Bernardino counties have experienced a boom in new apartment construction that dumped nearly 5,000 units on the market in the last 12 months. "There has been more new supply in the past year than in the past five years," said Delores Conway, a USC economist. "With this much supply, the demand has not been as strong." The occupancy rate in the Inland Empire fell to 93% in the second quarter from 94.9% a year ago, according to data being released today by RealFacts, a Novato, Calif.-based research firm. Experts say occupancy of 95% or better is necessary for a building to be considered fully occupied.