Child of “modest workers” in a communist country can have different meaning. Maybe they’re party elites? We don’t know. Something just doesn’t add up though.

In another article he writes: "In China, where I was born, there are a lot of people who work much harder but could not enjoy similar results. The difference is that I was lucky enough to have had the chance to move abroad at a young age, thanks my parents. In other words, as Warren Buffett said, a large part of life is the lottery at birth."

http://www.economist.com/whichmba/mba-diary-standing-oration

He's using the word "modest" to mean "not particularly prestigious" as opposed to "poor".