The number of cash-balance pension plans almost doubled between 2001 and 2006, growing to 3,588 nationwide, according to a survey by Kravitz, which designs and administers the plans. Officials at the firm witnessed exponential growth in the number of plans since the Pension Protection Act was passed in 2006, said Kravitz spokeswoman Meghan Conboy. The survey, conducted by reviewing companies' IRS 5500 forms, found that 75% of cash-balance plans had assets of less than $1 billion as of Dec. 31, 2006. The majority of cash-balance plans are in the medical and manufacturing sectors, with 28% and 14% of all such plans, respectively. California has the most cash-balance plans, at 462, followed by New York (405), Ohio (293), Illinois (253) and New Jersey (237).