In my experience, less than 5% are actually writing algorithms and solving harder problems. I work at a consulting firm with 100 or so developers, and most seem to do "simple" stuff most of the time.

The most complex thing I have heard of is someone who wrote a kalman filter thing for some part of a nuclear reactor. To me it seemed hard since I don't understand the math, and apparently people around him was happy with his solution.

Also here in Sweden I don't think the CS algorithms are very important at all when getting a job. I have just not seen it that much, which is sane since nobody seems to really need it anyway...