boil down to ~

ヨーロッパへの難民が急増しています。記事はCNNからの引用です。
今回は（基本的な表現ですが）boil down to ~を取り上げます。辞書にはboil down to Aで「〈状況問題などが〉つまるところAになる」とありました（『プログレッシブ英和中辞典』小学館）。鍋で煮詰める様子をイメージすると理解しやすいですね。（Koyamamoto）

Are countries obligated to take in refugees? In some cases, yes
(CNN)Hundreds of thousands of migrants are pounding on Europe's invisible doors -- dirty, exhausted and desperate to escape the daily carnage in their homelands.
But their arrival also puts a strain on European resources. Germany expects to take in 800,000 refugees and says it will spend at least 6 billion euros ($6.7 billion). Austria, which received 16,000 migrants in just two days, said it won't be able to keep up with this pace.
At the same time, several oil-rich Arab nations closer to the conflict zones have come under harsh criticism because they've taken in virtually no refugees.
So are countries obligated to house refugees? If so, why?
For the most part, it boils down to an international treaty.
http://edition.cnn.com/2015/09/08/world/refugee-obligation/index.html