The Dow closed above 14,000 for the first time in over five years on strong auto sales and optimism about US jobs. The index is just 155 points away from its highest close ever. But market watchers were divided over what the mark really means. To some, it’s an important psychological booster, making investors feel optimistic. But to others, it’s just a number, a sign more of how traders feel than of the economy. Drug maker Merck fell as fourth-quarter profit suffered because of competition from generic medicines against its blockbuster allergy drug Singulair. And Zoetis, an animal health business that Pfizer just spun off, rose 19 percent on its debut.