Ideally, the design of a building would create multiple switches for the overhead lighting. Adjusting these settings would allow the optimal light intensity to be delivered, the most common version of this control being the "three-level switch", also called A/B switching. Much of the benefit of the excess illumination reduction comes from a better ratio of natural light to fluorescent light that can result from any of the above changes. Research has been conducted showing worker productivity gains in settings where each worker selects his or her own lighting level.