Improved fourth-quarter sales and increased margins gave AutoZone Inc. improved quarterly returns, but annual sales still fell short of analyst expectations. For the quarter, net income rose to $213.5 million, or $2.92 a share, from $206.6 million, or $2.66 a share, a year earlier. Excluding charges, adjusted net income was $2.96 a share. Sales rose 3% to $1.94 billion, short of the $1.98 billion analysts had expected. All figures in U.S. dollars. Sales at stores open at least a year, a key measure in the retail sector, fell 0.9 percent. Notably, retail sales were up 3% in the quarter, which more than offset the 3% drop in commercial (trade) sales that makes up the minority of business for the chain. AutoZone reported that sales per average store slipped to $497,000 from $512,000. Shares of AutoZone closed at $94.10 Monday on the New York Stock Exchange. Through Monday, the stock was up about 2.6% since the start of 2006. Higher fuel prices and economic uncertainty have contributed to keep results across the sector depressed.