many ppl use multiple monitors these days (Score 1)

there are many arguments you can make here.

citing some arcane study may not have the impact you are looking for.

cost benefit analysis is what a company wants to see

so you argument should be

cost: 0 , monitor was discarded

benefit 1: "This has made it much easier to do my job"
benefit 2: if work is easier, i should be able to do more of it in the same time frame

argument 1: even if its only a 1% increase in productivity it is worth it, because the monitor cost 0

argument 2: this is also a perfect oportunity to study the benefits of addtional monitors, and possibly decide if purchasing them are worth it also

argument 3: CSI has tons of monitors, and they always get the job done in less than an hour

argument 4: with 2 monitors i can actually do work, while waiting for a group in World of Warcraft