I was reading an article on NHK easy news about whooping cough and I came across this sentence, 去年１年でこの病気になった人と同じぐらいです。I've seen this usage of "time duration" before but I never understood why just saying 去年で wouldn't be sufficient/proper (or perhaps it is. I'm not sure).
My question is what purpose is this for? If 去年 is already there, wouldn't the reader know that the writer was referring to the people who got sick last year?
Somewhat of a side question too, but is と's usage here used for comparing and contrasting? This year vs last year. I don't believe its usage is for a conditional and it isn't for connecting two nouns.
As always, thanks for any help that comes my way. I'm truly grateful.