収穫 しゅうかく逓減 ていげんじゃなかったです
shūkakuteigenjanakattadesu

Noun
Desu Copula

The polite, past negative form of 収穫逓減

1. Wasn't diminishing returns.; Wasn't a decreasing harvest.

Past/Perfective
Negative
Polite
Casual Register
Economics