On Sunday afternoon, Kate Middleton wore a $69.90 blue summer dress from budget retailer Zara. By Sunday evening, the dress was sold out.

Several fans lamented on Twitter about not being able to buy the highly-coveted garment.

Though true fans should not be surprised that an outfit Middleton wore instantly sold out. The “Kate effect," as it has been called, is not uncommon to the Duchess of Cambridge – for whom the phenomenon is named.

The mom of three wore the blue and white striped mid-length dress while she was on an outing with her two older children, Prince George and Princess Charlotte, to watch Prince William compete for the Maserati Royal Charity Polo Trophy at the Beaufort Polo Club.
这位三个孩子的母亲带着两个较大孩子出游,身穿长度中等蓝白条连衣裙的她,在保佛马球俱乐部(Beaufort Polo Club)出席玛莎拉蒂皇家慈善马球杯比赛(Maserati Royal Charity Polo Trophy Match)。

Though Middleton was praised for her fashion sense – the mom was ridiculed on Twitter for allowing her son, Prince George, to play with a toy gun during the outing.

Her sister-in-law Meghan Markle also experienced some Twitter backlash over the weekend for wearing an off-the-shoulder blush dress to the Queen's birthday parade.