Which file compression software for Linux offers the highest size reduction for source code?

I do a ton of file compression. Most of the stuff I am compressing is just code, so I need to use lossless compression. I wondered if there was anything that offers a better size reduction than 7zip. It doesn't matter how long it takes to compress or decompress; size is all that matters. Does anyone know how the various tools and compression algorithms available in Linux compare for compressing text? Or is 7zip the best for compressing source code?