収穫 しゅうかく逓減 ていげんではありませんでした
shūkakuteigendewārimasendeshita

Noun
Desu Copula

The polite, past negative form of 収穫逓減

1. Was not decreasing returns.; Was not diminishing returns.

Past/Perfective
Negative
Polite
Formal Register
Economics