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We may never know if St. Valentine, a martyr beheaded for officiating the forbidden weddings of persecuted Christians, was keen on chocolate and flowers. But we do know that millions of people around the world will be using those very items to celebrate his name on February 14.

In the UK, it is estimated that of the population will celebrate Valentine's Day this year, each spending around £52 on . The total spend in the US will be about US$27 billion (£22 billion), including roughly US $500 million on roses.

So the tradition of spending money on your romantic partner on February 14 seems fairly well established. But it is hard to know exactly when the link began.

Up until the late 14th century, Valentine's Day was solely a commemoration of his martyrdom. The shift toward an association with romantic love emerged in the Middle Ages, and is often attributed to the poet Geoffrey Chaucer, who linked Valentine's Day to romance in his poem "Parliament of Fowls."

But it was the 19th-century industrial revolution that brought about the mass production of romantic gifts. Cadbury was the to commercialize the association between romance and confectionery by producing heart-shaped boxes of chocolates for Valentine's Day in 1868. These boxes were decorated with images of Cupid, roses and hearts, and would sometimes be kept to store romantic letters and mementos.

While Hallmark did not invent the occasion, it played a big part in bolstering its popularity by selling Valentine's Day postcards in 1910, and then greeting cards from 1916.

Now in the US, around Valentine's Day cards are exchanged each year, making it the second largest annual occasion for card giving (after Christmas).

But it's not just car sellers, florists and chocolate-makers who seek to benefit from the commercial opportunities Valentine's Day provides. This year, for example, has partnered with a dating app to give nine British couples a "once-in-a-lifetime" first date in an Ikea store, where they will share a meatball dinner for two in bed.

Lego has launched a in major cities around the world to show off its floral designs, and Coca-Cola has teamed up with a fast-food brand to create a Valentine-themed .

Chocolate and marshmallows

These kinds of one-off marketing campaigns are only possible thanks to a long history of Valentine's traditions, which vary around the world.

In Japan, for example, it is a two-part celebration. On February 14, women often give "Giri-choco" ("obligation chocolate") to friends and colleagues, while "home-choco" ("true-feeling chocolate") is reserved for romantic partners. On March 14, known as White Day, men reciprocate by giving jewelry and less-expensive gifts that are white ( are a popular choice).

Celebrations in South Korea are similar to those in Japan, but with the addition of on April 14, when single people gather at restaurants to eat black noodles (jajangmyeon). In the Philippines, Valentine's Day is marked by mass weddings organized by the government.

In Finland and Estonia, Valentine's Day is known as "Friends' Day" with the focus on celebrating non-romantic love and friendship. A similar idea, , which featured in a 2010 episode of the US sitcom Parks and Recreation, has become a popular way of celebrating female friendship.

Love for sale

Of course, not all consumers enjoy Valentine's Day rituals. For many, there is pressure attached to romantic shopping, while for others it is just an unwelcome reminder of their single status.

It can also bring social pressure, and lead to feelings of .

But there is a market . Anti-Valentine's day sentiment has inspired other ways to (not) celebrate, including a aimed at single people.

It can also be a very valuable day for businesses, large and small. With high and , Valentine's Day brings a major surge in revenue for sectors including retail, hospitality and entertainment.

So, although it might not sound very romantic, it's worth remembering that while money can't buy you love, love can provide a significant boost to the economy.