When do you use the before plural demonymic expressions like "Americans", "British people" or "Chinese people"?
Chinese people celebrate Lunar New Year on the first days of the first lunar month.
The Chinese have been maintaining a form of state-sanctioned capitalism.
The Chinese people shall maintain our cultural identity against western encroachment.
Americans often love to espouse freedom.
The Americans had no choice but to interfere in the War.
These people have actively pushed for policies that are against the expressed wishes of the American people.
To me, it seems to work like this
- Without the: when you're talking about other peoples and their foreign cultures
- With the: when you're contrasting one people with another ("the Americans did this while the Germans did that")
- With the and people: when you're talking about your own people
Note: Please refrain from irrelevant discussion on parts of speech. This question is not at all about whether Chinese in the Chinese is strictly an adjective, or a collective noun. What this question concerns is semantic differences that could arise due to the presence or absence of the article the. Again, it is not about the adjective-vs-noun debate (note how Americans is undoubtedly not an adjective), unless that debate is not wholly grammatical, but indeed productively helps explain the semantics.