Google published a study last Thursday on how in-store shoppers use smartphones.

The study is useful for marketers to understand how smartphone users use search and other features while shopping in stores. The key takeaways are:

79% of smartphone owners are ‘smartphone shoppers’
84% of these shoppers use their phones to help shop while in a store
The average time a smartphone shopper uses their phone in a store is 15-minutes
Shoppers who use their smartphones typically buy more while in the store
Consumers choose search as their number one in-store resource to help make purchase decisions, followed by store web sites and brand web sites

Here is the study:

I recently leased a new car and I sat in the sales negotiation area on my smartphone searching Google for what others were able to lease the same car for. I was able to negotiate a much better lease rate because I had my smartphone and I ended up walking out with the car I wanted, paying a heck of a lot less than I could have imagined.

Forum discussion at Google AdWords Help.