1. It is extremely difficult to estimate the true value of the services which people perform for us.
    但要估算别人为我们为所提供的服务的价值却是极其困难的。

2. We already see that. One recent estimate is that one-sixth of all fourteen- to twenty-four-year-olds in America — mostly males — are currently "disaffected and disconnected".
    我们已经看到了这一点。最新的一项估计表明，美国所有14至24岁的人当中有六分之一--大多数为男性--现在已 "心存不满，与社会格格不入"。

3. This is a conservative estimate of the population in the year 2000.
    这是对公元二○○○年时人口的保守估计。