how many papers important results are simply bugs?

Numerical code is already bug prone due to subtle and hard to test errors, research code that's not code reviewed or necessarily even tested for correctness can easily generate important results erroneously.

It's also counter-productive not to publish the underlying source code for these papers, as it adds a barrier to other researchers applying the algorithm in new situations. I'd be interested in seeing if those 6% of papers which include the code get more citations than the population of papers which do not include code.