From the Consumer Psychology website, this section on Smart Shopping Insights:

Key Insights
Consumers should be aware of the fact that labels containing statements such as, "12 for the price of 10", or "3 for $1.99" can increase sales in at least 40%. Learn More...

Products in large packages are perceived as less expensive to use, so consumers used them 18% to 45% more than usual. Learn More...

In a focus group, 84% of the people agreed with the belief that "More is Better" when dealing with consumer products such as detergent. Learn More...

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