Tracking a subset of firms with 20 percent or greater representation of women in top executive roles in the year 2000, we report that these firms continue to have a higher than average percentage of women in top executive roles in 2015. Gaps in the pipeline, even at these best practice firms, suggest more needs to be done to ensure a steady flow of future women leaders. Executives at these best practice firms report that sponsorship from top leadership has been key to their high levels of women in senior roles. We discuss the implications of these findings for the progress of women in the pipeline and argue that firm-level commitments to diversity by top corporate leaders are essential for further progress.