JPG files use 8 bits per color per pixel (I've never heard of any camera that uses the alleged 12-bit-per-color-per-pixel extension) and is a compact way of storing images.
RAW files are huge but have the full image data from the image sensor which is likely to be more than 8 bits. (judging from recent DSP specs I would assume 12 bit ADCs are the norm... but how would you actually find out how many bits a particular camera provides?)
Is there anything similar to JPG which stores the file in a form that allows lossy compression for high spatial frequencies, but has more dynamic range than 8 bits?