Demand for diamond jewellery was less than sparkling last year, highlighting the challenges facing the world's largest producers as they ramp up advertising in an effort to woo millennial buyers and fend off the threat of artificial lab-grown stones.
Global demand rose 0.3 per cent to $80bn as the industry's brightest growth hopes — China and India — wobbled last year, hit by a strong dollar, slowing spending, India's demonetisation programme and a month-long strike by the country's jewellers.
The figures, in a report commissioned by De Beers, the world's largest diamond producer, show the US was the one bright spot, with demand rising 4.4 per cent year on year.
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The data come as the industry is boosting marketing spend in the hope of winning over new consumers as well as the millennial generation, who view jewellery differently from their predecessors and are marrying later.
Last month De Beers said it would invest more than $140m in marketing during 2017, its biggest spend since 2008. That comes alongside a $60m marketing spend by the Diamond Producers Association — four times its 2016 budget. The group was formed in 2015 by seven of the world's largest producers, including De Beers.
The company, which invented the slogan "A Diamond is Forever" in the 1940s, is aiming to shift the association of diamonds with marriage to include other life events as well as targeting the growing spending power of women.
One-third of all diamond jewellery in the US, outside of the wedding market, is bought by women for themselves, up from 23 per cent 10 years ago. The US accounts for 47 per cent of all global sales.
"The self-purchasing element is a whole new angle on potentially a bigger market and a potentially new source of demand," said Bruce Cleaver, chief executive of De Beers. "I don't think the core of the business, which is diamonds as a gift, is likely to change but this is an enormously powerful potential additional source of demand."
De Beers also faces the challenge of lab-grown diamonds, which are made by layering carbon on to a diamond seed and mimicking the high temperatures that create natural diamonds in the earth. Lab-grown diamonds comprise about 2 per cent of diamond sales but are estimated to account for 10 per cent of supply by 2030, according to analysts at Citi.
Mr Cleaver, however, shrugged aside the threat.
"There is a place for synthetics, perhaps as a fashion item, but there is nothing rare about them and they are not diamonds in my book," he said. "It's a traditional question I know, but if you ask a lady would you like to be given for your engagement gift a natural diamond made by the miracle of nature 4bn years ago or something made in a press last week, its pretty obvious what the answer is."
Mr Cleaver also said there had been promising signs this year from China, the world's second-largest market, where listed Chinese jewellers have reported stabilising sales.
In 2016 China sales rose 0.6 per cent in local terms but dropped 4.8 per cent in dollars as the renminbi weakened — a contrast to the previous decade when sales grew at a compound rate of 12 per cent a year.