A shock reverberated through the real estate industry last week when the National Association of Realtors settled a lawsuit by home sellers who claimed the group's long-running practice of setting 5 to 6 percent standard commissions on home sales amounted to price fixing. The NAR agreed to end its rules requiring that standard commission and for the commission to be split between the seller's agent and the buyer's agent. Real estate agents, already struggling with a market where few homes are available for sale, will almost certainly see their commissions shrink as they compete for listings.