The study examined 60,000 campaigns across over 20 countries. 

It found that only 50% of ad impressions served in the UK that were meant for women were served to women, compared with 62% success with targeting men. 

The difference was even greater when targeting 18-34 year-olds, with just 22% successfully reaching women and 33% reaching men. 

Overall, only 54% of ad impressions were delivered to the audience they were intended for. 

Targeting success varied by sector: travel and business/ consumer services marketers were the most likely to reach their desired audience ( 67% for both), followed by entertainment ( 65%). Retail ( 42%) and FMCG ( 43%) marketers struggled most to reach their target audience. 

Meanwhile mobile outperformed desktop on targeting, with a higher on-target hit rate for six of the nine age breakdowns. This medium was also the only area where advertisers are better at targeting women than men: among mobile campaigns targeted at 25-44 year-olds, 37% of impressions were successfully served to women, compared with just 22% among men. 

“Online advertising has plenty of room for improvement in hitting advertisers’ desired audiences, particularly women,” said Barney Farmer, Nielsen’s UK commercial director.

“Various things that can make a difference are better use of the available technology, incorporating wider sources of data, particularly first party data, as well as buyers taking more action on the insights they’ve got from previous campaigns to improve future results.”