Meaning of のだろう?

Question

I'm not sure when should I use particle の in front of だろう/でしょう? Is のだろう used when the speaker wonders about something to himself? For example, what would be the translation of these sentences: > 日本は、これからますます高齢化が進むだろう。 > It seems that lately the aging in Japan is increasing. > 最近、デパートの売り上げが伸びている。景気が回復しているのだろう。 > Store's sales increased. I wonder if the business is recovering? > 何をするのだろうか。 > What could I do?

Answer 1

It is like the difference between です and んです (のです), A sentence with です is just a simple statement. んです indicates when you explain or emphasize the statement, We also use んです when we want to say something more about what we have just said in the statement.

Now, here is the difference between だろうand のだろう.

The sentence,「日本はこれからますます高齢化が進むだろう」,indicates that you "just guess" about the statement inside the quotes. "I think that the aging in Japan will be increasing more and more in the future,"

For this statement,「日本はこれからますます高齢化が進むのだろう」, has more comments about it. Usually, it has a hidden message. Some people may continue 「だから、景気が悪くなる」"That's why the economy gets worse." or 「だから税金が高くなる」"That's why, the tax will be more expensive."