Officially, it's all of them. From title 18 section 3553 of the US code:
> The court, in determining the particular sentence to be imposed, shall consider ...
> (2) the need for the sentence imposed—
> (A) to reflect the seriousness of the offense, to promote respect for the law, and to provide just punishment for the offense;
> (B) to afford adequate deterrence to criminal conduct;
> (C) to protect the public from further crimes of the defendant; and
> (D) to provide the defendant with needed educational or vocational training, medical care, or other correctional treatment in the most effective manner;
This is surprising to me. In Germany, the constitution (as the highest law) is clear on the issue: punishment is not a goal, only deterrence of also the violator but especially others. I guess it is because the constitution here is quite new, compared to US. Funny tho, as I believe the US played an important role in drafting it.
> The court, in determining the particular sentence to be imposed, shall consider ...
> (2) the need for the sentence imposed—
> (A) to reflect the seriousness of the offense, to promote respect for the law, and to provide just punishment for the offense;
> (B) to afford adequate deterrence to criminal conduct;
> (C) to protect the public from further crimes of the defendant; and
> (D) to provide the defendant with needed educational or vocational training, medical care, or other correctional treatment in the most effective manner;
https://www.law.cornell.edu/uscode/text/18/3553