In 1974, Kawasaki introduced the Jetski, a revolutionary jet-propelled, single-person watercraft capable of speeds up to 40 mph. Based on the concept of a motorized waterski, the original Jetski required the rider to stand and use considerable strength and balance for control. It was not until 1986, when Yamaha introduced the Waverunner, a more manageable sit-down version, that "personal watercraft" gained widespread appeal. Within ten years, it blossomed into a $300 million a year industry with annual sales over 200,000 in the United States alone, and led to the creation of two competitive Jetski racing circuits. But in the late 1990s, increased complaints about safety, fuel emissions, and noise resulted in a public backlash. Several states enforced mandatory driver's education and minimum age restrictions, and some areas, including Lake Tahoe, the San Juan Islands, and the majority of the National Parks, banned the craft outright. Industry experts agreed that the continued popularity of personal watercraft would depend on improved driver education and cleaner, quieter engines.