Abstract: Notions of "good practice" exist for many aspects of a programmer’s work. They are intended to bring benefits on a variety of dimensions from the most concrete and measurable, such as program speed, to more subjective characteristics such as readability. This research addresses programmer practices good or bad in any part of their professional work but considers them from the perspective of a single outcome: impact on the productivity of fellow programmers. The findings are now being applied in an experimental new framework for professional development.