I haven't the slightest idea. I do think it's interesting that in Vietnam, it's the year of the Cat. In Chinese mythology, the cat doesn't have a place in the Chinese zodiac. Many years ago, the Jade Emperor declared a great race would be held to determine positions in the zodiac. Rat was supposed to wake Cat the morning of the race, but he didn't - and thus, Cat slept through the race and lost his chance to compete. He hates Rat to this day. I wonder why Cat get a place in the Vietnamese calendar. Do they not have rabbits in Vietnam?
According to ChineseFortuneCalendar.com, 2011 is the year of the Metal Rabbit, that is, the year of the Yellow/Gold/White Rabbit. It's a strong 'wood' year (tying into the five elements) and a good romantic year for Horses, Dogs and Tigers. Unfortunately, if you were born in the year of the Chicken, your romantic life and social relationships are going to suck in 2011 because Chickens are the enemy of Rabbits.