In the last ten years, the gap between wealthy people and poor people has increased rapidly.
この場合、次のような言い方ができますよ。
ーIn the last ten years, the gap between wealthy people and poor people has increased rapidly.
「ここ10年で貧富の差がみるみる拡大した」
the gap between wealthy people and poor people「貧富の差」
rapidly「みるみる」と言えます。
ここでは現在完了形を使うと良いですよ。
ご参考まで！
カナダ 
