SEATTLE, WA: Digital ads are prompting US shoppers to raise their purchase and average spend rates, with warehouse clubs and dollar stores leading the way, according to a new location metric.

Placed, a mobile-location analytics firm, used its new Placed Revenue tool to examine more than two million first-party survey responses in Q2 2015 that were linked directly to measured store visits, combined with data from third parties.

It concluded that shoppers at leading warehouse clubs, such as Costco and BJ's, spend considerably more per visit than at the average retailer and that shoppers at dollar stores are at least 30% more likely to buy, Advertising Age reported.

Warehouse clubs topped the list for average spend with Costco (149%), BJ's (137%) and Sam's Club (136%) indexing comfortably above the average of all stores in the study.

Consumer electronics retailer Best Buy (140%) and furniture retailer IKEA (132%) also performed well for average spend, while fashion retailers, such as Nordstrom, Macy's and others, featured strongly in the inaugural top 20 from Placed.

Turning to consumer purchase rates, the report found that four dollar stores featured in the top ten and that their low price point represented a low barrier to purchase.

99 Cents Only indexed 136% above the average retailer, closely followed by Dollar Tree (132%) and Dollar General (131%). Family Dollar (125%) was ranked seventh.

Wholesale clubs also featured strongly in terms of purchase rates and they included BJ's (128%), Costco (127%) and Sam's Club (124%).

Also, giant discounters Walmart (124%) and Target (122%) made the top 10 along with Meijer (129%), the Michigan-based hypermarket chain.

David Shim, founder and CEO of Placed, stated that the company's Placed Revenue tool could help digital advertisers when trying to calculate their ROI.

"Placed Revenue brings the measurability of the digital world to the physical when calculating the return on investment associated with digital advertising," he said.

Data sourced from Placed, Advertising Age; additional content by Warc staff