A "major business expansion" is defined as a new lease of at least $1 million in value or of 20,000 square feet of space or more. Those aren't really considered "major" numbers, but they give the Los Angeles County Economic Development Corp. an idea of who is doing what, and where. (For every major expansion, there are three others not tracked.) Anyway, the new EDC report finds that L.A. County had a 22.5 percent drop in such expansions last year, not surprising given the deteriorating economy. OC was down 10.1 percent and Riverside-San Bernardino down 30.8 percent. The "professional services" category - that covers accounting, law, architecture and engineering - led the way in major expansions for L.A. County.