Maintaining stroke weight proportionally in scales

when i give a path a stroke weight and then scale and then scale it down, the stroke weight remains in the same. how can i get the stroke weight to scale proportionally too.

example: when I make a logo, I assign a stroke of 2 pts to the graphic. then I scale it down to a business card size and the stroke weight remains 2 pts which is too much for a tiny graphic. also when I scale it up, the stroke weight proportionally appears to be too thin... please help