"necessary contribution" is a correct and usable phrase in written English.
It is typically used to refer to the idea of making a meaningful contribution that is needed or required in some capacity. For example: This project requires all team members to make a necessary contribution in order to be successful.
If a 'ride' costs £10 and I contribute only 50p, my ride is not literally free but, nevertheless, by shirking part of the necessary contribution I may be committing an injustice – as are those who refuse to contribute what is necessary to maintain the institution of research, even if they have paid something towards it in some form.
It is a huge and very necessary contribution to our understanding of this obscene subject.
It was an important and necessary contribution to Vivid, given gaming's growing cultural impact and its Hollywood-rivalling scope.
Quoting Aristotle, he said "repugnance makes a necessary contribution to the good life, especially when there is not time for intellectual evaluation".
Indeed, he almost seems to welcome scepticism as a necessary contribution to Neurosis's performance, since all great fairground experiences depend, for their effect, on a measure of the improbable or incredible.
She said the detail on who would make payments had been left open in order to ensure that all those factory owners who could afford to pay for repairs and compensation for workers made the necessary contribution.
And on four of the CD's 14 tracks, Dorothea Röschmann, a fine soprano, makes minor but necessary contributions.
If they're not producing, they're not making the necessary contributions to society, and so they're devalued".
If individual countries are no longer able to make the necessary contributions, others must do so on their behalf.
I don't expect I'll get a pension because I can't afford to make the necessary contributions to the fund – if I pay, I can't afford to live.
This study investigated the neural systems that may make necessary contributions to the retention in working memory of location information.
