Office Depot posted a loss in the first quarter and said it would close at least 400 U.S. locations, starting with 150 this year. This is not so different from what Staples said two months ago. It is a reaction to a broad declining trend in office paperwork as more documents are handled electronically. Other trends are also working against the big-box office supply stores, besides the trend away from paper and toner: computers are more durable, office equipment generally is smaller, so that less furniture is required, and businesses are more flexible in the way they purchase supplies.