In Ontario, approximately 130,000 sleep studies were conducted in 2008, which is twice the number of sleep studies reported in 1999. In 2008, Ontario spent approximately $40 million on polysomnography (PSG) testing alone, despite the fact that access to PSG remained limited, with an average waiting time of approximately 3.5 months for an in-laboratory sleep study and approximately 12 months from referral to appropriate treatment. Portable monitors (PM) have been developed in an effort to substitute for the more costly and labor intensive clinic-based PSG. As of 2011, there are over 40 PM commercially available in the United States with different configurations for cardiorespiratory and neurophysiologic signals.