It has been frequently assumed, but not proved, that the majority of the migrants in what has come to be called the Great Migration came from rural areas and were motivated by two concurrent factors.

人们常常假设，但没有证据证明，在所谓的“大迁移”中，大多数移民来自农村地区，这是由两个同时发生的因素推动的。

youdao

We think of this as an old person's migration, but it created many jobs for the young in construction and health care, not to mention tourism, retail and restaurants.

我们认为这是老年人的迁移，但它在建筑和医疗保健领域就为年轻人创造了许多就业机会，更不用说在旅游业、零售业和餐饮业中了。

youdao

In addition to all that, it is not even clear that assisted migration or any migration for that matter, will help at least for some species.

除此之外，我们甚至不清楚辅助迁移或任何相关的迁移是否至少对某些物种是有帮助的。

youdao

"They are not looking to hire as many immigrants. So this is the first thing that reduces the level of migration.

VOA: standard.2010.01.20

"The first thing that affects migration is the fact employers do not want as many workers,".

VOA: standard.2010.01.20

Historically most urban growth has been due to natural increase, not migration.

ECONOMIST: Cities

Immigration minister Damian Green said he had decided to extend the restrictions as he wanted to ensure migration from those countries delivered economic benefits to the UK and that he did not want migration to have adverse impacts on the domestic labour force.

BBC: Restrictions on Bulgarian and Romanian workers extended

Many of the economic gains from mobility do not require migration to be permanent.

ECONOMIST: Managing the market