In addition to solving the problems of flicker, electronic ballasts also provide other advantages over magnetic ballasts. With a square wave voltage, the cathodes spend much more time emitting electrons and exciting the plasma, creating a gain of 5–10% in lumen output. The square-wave nature of the power flow allows lamp life to be extended by as much as 20%. Most modern ballasts are now also equipped with a dimmer, which uses pulse-width modulation to dim the lamp up to 50%, or as much as one stop of light. Unlike a tungsten-based light, which has a negative color temperature shift with a drop in power, the mercury emission spectra takes over with a drop in power (approximately 200 K bluer at 50% output).