Each year global estate agency Knight Frank publishes its Wealth Report, revealing which assets have increased most in value and which haven't done so well. From ceramics to art, here's how 10 investments have performed, making the rich even richer.

At the bottom of the table are Chinese antiques. Be very wary when purchasing these pieces. Over the last decade their value went down to -4%, and in 2018 they actually lost value (-2%). If you are looking to buy, stick to Ming and Qing dynasty pieces as they historically have more lasting value.

Once fashionable, Han to Yuan dynasty pieces, like this kiln, have lost value in the last decade. When investing in antique Chinese ceramics, oldest tends to be better, but always watch out for fakes.

As well as being pretty, jewels can be an excellent investment. Though jewellery had a 0% change in 2018, over the preceding decade it dipped slightly with a worth of 125%.

Art Deco and Belle Belle Epoque pieces are also doing well, almost doubling in value over 10 years. Those investing in jewels should be careful though; the condition of the piece, provenance and style will all influence its worth. What you consider to be most beautiful might not be the most sellable.

In 2018, the value of antiques shrank to 1%. Early to mid-20th century pieces lost the least value in the past few years.

Regency-era pieces from the 19th century have dropped most. However much you love them, they have sadly fallen out of fashion and so has their value. These once revered items lost 32% of their value in the past 10 years.

Coloured diamonds may have only grown 1% in 2018, but over the decade their value has soared by 85%; much more than their clear cousins. The Oppenheimer Blue, a 14.62-carat diamond, was sold by Christie’s Geneva for almost $58.8 million (£46m) in 2016, making it the most expensive jewel to ever sell at auction, and underlying the popularity of blue stones.

Yellow diamonds saw their value increase by just under 50% in the decade to 2018. So, when choosing your diamonds, remember colour can matter just as much as size.

Though the value of stamps only increased in value by 1% in 2018, it doesn’t mean you should stop filling up your stamp book. Over the previous decade, their value grew by 103%.

But while they are a good investment for passionate collectors, stamp firm Stanley Gibbons advises that they should not make up more than 10% of any investment portfolio.

While they're a popular collector's item, the value of coins slipped down the rankings to fifth, rising by 4% in 2018, and 182% over 10 years.

However, coin collecting is generally considered to be a safe investment as the pieces will always be worth at least as much as their weight in precious metal. Though their returns are much smaller than items further up the list, they are certainly steady.

Watches can make or break an outfit, but they also make very steady investments. In 2018, their value went up by just 5%, but they have grown by 73% over the past decade. Experts advise you to save all of the boxes and paperwork, as this will help boost their resale value down the line.

Rolexes are the most accessible fine watch brand, but you'll get better returns with classic Cartier models. Though watches have sentimental value, their worth has not increased nearly as much as some of the goods further up the table.

The value of classic cars has been motoring away. Over the past year, the value of vintage motors increased at a respectable 6%, and up 289% over the 10 years to 2018, according to Knight Frank.

So what kind of classic cars might the mega rich (or 'ultra high net worth individuals' as they are called) look to invest in? A 1962 Ferrari 250 GTO (like this one pictured) sold for a staggering $48 million (£37.8m) at Sotheby's in August 2018, making it the most expensive car ever sold at auction.

Wine is the second best luxury investment with 7%, according to Knight Frank's 2018 Wealth Report. It is, however, down from first place in previous years.

“This year has been about consolidation,” says Wine Owners’ Nick Martin. “Some of the more expensive, older vintages are coming off their peaks, while others power ahead. Burgundy continues to defy gravity as it adds another 14% in the year to date, compared with Bordeaux first growths at less than 3% overall."

Art surged to the top of the luxury investment index, with a huge annual growth of 25% in 2018. Given the $450 million (£353.8m) sale of Leonardo da Vinci’s Salvator Mundi in 2017, it is unlikely that we will see a new record price for a painting any time soon, however.

Modern art lovers, you could be in for a treat as this style has doubled in value over the past 10 years. Art can be a tricky investment, as it is closely linked to trends and fashions, which are often unpredictable. Experts advise to only buy what you love – if the value drops, at least it will still look good on your wall!