About half of the top 200 U.S. law firms display pop-up messages asking if viewers consent to cookies, but that number rises to more than three in five of the top 50 firms, according to a new Bloomberg Law survey.

The survey also found that of the roughly 100 firms that do provide options for viewers’ consent to cookies on their Internet home pages, almost 80 boast at least one European office.

The growing use of consent notices for cookies—pieces of data that are sent by websites and stored on the user’s computer by their Web browser—is most often attributed to the European Union’s General Data Protection Regulation, commonly known as the GDPR.

The higher consent rate for firms with a European presence may make sense because of a need to comply with the GDPR, the survey found.

“I was kind of surprised that a higher percentage” of law firms surveyed didn’t ask the cookie consent question, said Bloomberg Law legal analyst Mark Smith, the author of the analysis, because “these are large, international law firms” that presumably are interested in soliciting European and other overseas business.

Of the firms that use cookie consent pop-ups, almost four in five, 78 percent, placed them at the bottom of the home-page screen, the survey found. A smaller percentage, 14 percent, put the banner notice at the top of the screen. The survey looked at the firms listed in the most recent AmLaw 200, which ranks law firms by gross revenues.

Smith said he was also surprised at the percentage of law firm notices that used “ambiguous” language, which makes it more difficult for users to know if they’re allowing cookies or not when closing the pop-up. Such unclear closure options included the word “close” or simply an “X”.

Smith concluded that an older EU measure—the ePrivacy Directive—also plays a “significant” role in the growing prevalence of cookie consent notices.

The directive mandates that users “should have the opportunity to refuse to have a cookie or similar device stored on their terminal equipment.”