题目：
人口普查官员说，并不是所有这些迁移都是为了离开寒带，绵延不断的移民潮还有当年“生育高峰”时期出生的孩子已经到了生育年龄，这些因素都在起着作用。
此外，人口统计学家发现，向南部和西部的不断迁移还伴随着一种与此相关却又与以往不同的现象：越来越多的美国人显然不再只是寻找有更多就业机会的地方，他们还在寻找人口稀少的地方。请看下面的例证：
从区域上看，落基山脉附近各州的人口增长率最高——有报告说，居住在这片广袤地带的人口仅占美国总人口的5%，但自1970年开始，其增长率却上升到37.1%。
从各州情况看，内华达州和阿利桑那州是增长率最高的两个州，分别为63.5%和53.1%。除了佛罗里达州和德克萨斯州外，处于增长率前十位的是西部各州，共有750万人口——每平方英里大约9个人。
逃离人口稠密地区的做法改变了过去一味要离开寒带地区到气候暖和地方去的趋势。
1980年人口普查的统计数字最充分地描绘出美国人迁往最西部是为了找到更广阔的生存空间。这样一来，70年代加利福尼亚州人口增长最快，增加了370万。
答案：
参考答案：
Not all that shift can be attributed to the movement out of the snow belt, census officials say, nonstop waves of immigrants played a role, too, and so did bigger crops of babies as yesterday’s "baby boom" generation reached its child bearing years.
Moreover, demographers see the continuing shift south and west as joined by a related but newer phenomenon: more and more Americans apparently are looking not just for places with more jobs but with fewer people, too. Some instances—
· Regionally, the Rocky Mountain states reported the most rapid growth rate, CG.A percent since AIG0 in a vast area with only E percent of the US population.
· Among states, Nevada and Arizona grew fastest of all: FC.E and EC.A percent respectively. Except for Florida and Texas, the top A0 in rate of growth is composed of western states with G.E million people—about I per square mile.
The flight from overcrowdedness affects the migration from snow belt to more bearable climates.
Nowhere do AIH0 census statistics dramatize more the American search for spacious living than in the Far West. There, California added C.G million to its population in the AIG0s, more than any other state.
