Meaning of 減 in Japanese

この数字は原油輸入減を反映している。
This figure is a mirror of the decrease in imports of crude oil.

彼女は甘さ加減がよいかどうかケーキの味見をした。
She tasted the cake to see if it was sweet enough.

私は彼が笑っているのを見てやっと自分のばかさ加減に気がついた。
It was not until I saw him laughing that I realized what a fool I had been.

先進国では虫歯が激減し、自分の歯で一生食べられる人が増えています。
Cavities have become rarer in the developed countries and more people will be able to eat with their own teeth throughout their life.