"Multiple studies show that day lit stores have higher sales than their counterparts. The study below confirmed earlier findings showing stores with optimal daylighting can achieve 40% higher sales when compared to non-daylit stores."
Source: "Integrated Energy Systems: Productivity and Building Science" report prepared for the California Energy Commission Public Interest Research Program by the New Building Institute Inc., October 2003
"Skylights were found to be positively and significantly correlated to higher sales. All other things being equal, an average non-skylit store in the chain would likely have 40% higher sales with the addition of skylights, with a probable range between 31% and 49%. This was found with 99% statistical certainty."
Simply put, comfortable customers who see products in full spectrum full color rendering light translates to happier customers. Through daylight customers stay longer and return to the beautifully daylight space resulting in increased sales.
If your sales are impacted by your customers ability to evaluate your products in detail, then enhance the visual acuity through natural daylight.
An example specification for Sundolier in a retail setting: