1. When people in developing countries worry about migration, they are usually concerned at the prospect of their best and brightest departure to Silicon Valley or to hospitals and universities in the developed world.
解析：这句话虽然长，但主从句的界限很明晰，首先是when引导的时间状语从句，其次就是一个主句。难点在于主句宾语较长，需要进行意群切分，其正确的解读是：宾语的核心信息就是the prospect of their best and brightest departure，后面是两个介词to引导的地点状语，表示departure的方向。
2. These are the kind of workers that countries like Britain, Canada Australia try to attract by using immigration rules that privilege college graduates.
解析：本句主干为These are the kind of workers，主语these指代的是第一句中前往发达国家的本国人才。that引导的定语从句，修饰workers，从句的主语为countries，从句谓语部分为try to attract，后跟介词短语做方式状语，其中又套that引导的定语从句，修饰immigration rules。
3. A big survey of Indian households in 2004 found that nearly 40% of emigrants had more than a high-school education, compared with around 3.3% of all Indians over the age of 25.
分析：这句话的难点就在于省略结构，compared with之后省略了比较对象的核心概念“high-school education”。
4. They fear that it hurts their economies, depriving them of much-needed skilled workers who could have taught at their universities, worked in their hospitals and come up with clever new products for their factories to make.
解析：这句话有两个难点：一是出现了两个较长的从句，分别是that引导的宾语从句和who引导的定语从句，该定语从句中包含了三个并列的谓语成分。二是定语从句使用了虚拟语气could have done的形式，可翻译为“原本……”。
词组：deprive sb of sth剥夺某人某物；come up with想出，提出。