According to the 2014 ASI Impressions study.

For this study, respondents were asked to rate up to three promotional items they had received in the last 12 months.
Promotional items were defined as items that include pens, T-shirts, mugs, calendars or any items that have a logo or message from an advertiser on them; they are usually given away for free to consumers in hopes of positively influencing their purchasing preferences or their attitudes toward the advertiser.

As the chart below reveals, writing instruments were most commonly cited, as more then one-half (56%) of promotional product recipients in the U.S. reported getting at least one in the prior 12 months, followed by shirts (48%) and bags (34%).

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