I really appreciate your invitation, but I must decline it.

非常感谢你们的邀请，但我不得不谢绝。

youdao

Lizzie: Sir, I am honoured by your proposal, but I regret that I must decline it.

先生，我对你的求婚感到光荣，但很遗憾我必须拒绝。

youdao

Sir, I am honoured by your proposal, but I regret that I must decline it.

先生，你的求婚使我感觉荣幸，可惜我除了谢绝别无他法。

youdao

But if demographic decline is not generally a consequence of economic decline, surely it must be a cause?

ECONOMIST: Declining populations