Last December, Germany's federal anti-discrimination agency compared the prices of nearly 1,700 products that targeted a specific gender but were otherwise similar.
It found that women regularly paid more than men for the services of hairdressers and dry-cleaners. Almost nine out of 10 salons priced their services according to gender, and dry-cleaning a blouse costs on average €1.80 (S$2.85) more than the cost for cleaning a men's shirt.
It called for closer monitoring of gender price gaps in future and said consumers should be made more aware of the disparities.
To protest against gender discrimination, including the "pink tax", a group of South Korean women has decided to stop spending money on the first Sunday of every month.
The campaign, launched by a Facebook group called Female Expenditure Strike last month, aims for zero expenditure in a day to show how industries will suffer a considerable blow without female consumers.
The group has more than 5,000 followers on Twitter and more than 300 on Facebook.
In 2015, New York City's Department of Consumer Affairs studied gender pricing disparities between goods sold in the city.
It compared nearly 800 products with clear male and female versions from more than 90 brands sold online and in stores. It found that, on average, products for women cost 7 per cent more than similar products for men.
Across the entire sample, women's products were priced higher 42 per cent of the time, while men's products cost more 18 per cent of the time.
To highlight such disparities, Burger King posted a video on YouTube last month, which showed female customers being charged US$1.40 (S$1.90) more for an order of chicken-strip fries in a pink box.