许多人在19世纪通过移民来到美国寻求更好的生活。

Many people came to the US through ___immigration in the 19th century seeking a better life.

许多人为了更好的生活选择移民到发达国家。

Many people choose ___immigration to developed countries for a better life.

这个国家的经济增长很大程度上得益于其庞大的移民群体。

The country's economic growth benefits greatly from its large ___immigration population.