Earlier in 2017, Neha Kumar treated herself to an $8,000 pair of sapphire earrings to match a ring her husband gave her in 2012.

"I loved them and [they are] a unique piece," she said in an email to S&P Global Market Intelligence. "I mostly collect pieces because I have two girls, and I always think it's something to pass on to them as an asset/investment," said Kumar, who has worked in finance for over 10 years.

Kumar, who lives in Hong Kong, represents a new dynamic in the luxury jewelry market: Increasingly, women are buying more high-end jewelry for themselves. Economic independence, transformations in relationship dynamics and changes in perception are encouraging more and more women to buy their own items of jewelry.

De Beers, which produces and sells more than one-third of the world's rough diamonds by value, calls the trend "female empowerment." It is helping to drive demand in the luxury jewelry market, which has grown at an average annual pace of 6.8% over the past decade, according to Euromonitor International.

Between 2014 and 2016, women accounted for 23% of total diamond sales in the U.S., China and Japan, according to a Sept. 14 report by De Beers, which is owned by mining company Anglo American Plc. In contrast, diamond purchases made by spouses or partners accounted for 25% of total sales.

The theme is strong in the U.S., where women's self-purchases accounted for 33% of nonbridal diamond jewelry sales in 2016, up from 23% in 2005.

De Beers attributed the fashion to couples marrying later in life and stronger female independence resulting in modern relationships. The factors are changing the motivation for jewelry purchases, with more women buying or receiving diamonds for spontaneous moments rather than relationship milestones, it added.

"The trend towards greater female empowerment is only set to grow further," De Beers Group CEO Bruce Cleaver said in the report.

The global fine jewelry market, comprising items made from precious metals and gemstones, has shown a pattern of consistent growth over the past decade, almost doubling in size in terms of value, according to data compiled by Euromonitor for S&P Global Market Intelligence. The market research company estimates fine jewelry sales will expand by 4.0% year over year in 2017 to $268.6 billion from $258.15 billion in 2016.

Compagnie Financière Richemont SA, the Swiss luxury goods company that owns jewelry brands such as Cartier, Van Cleef & Arpels and Piaget, saw sales in its jewelry maisons, or houses, jump 17% in the five months ended Aug. 31. It declined to provide further details. French luxury goods giant LVMH Moët Hennessy Louis Vuitton SE saw revenue in the watches and jewelry business rise 13% in the first nine months of 2017.

The brands' luxury jewelry pieces command a wide range of prices. Cartier offers its gold and diamond Amulette de Cartier necklaces for as little as $1,890, while its Agrafe necklace range, also made of gold and diamonds, costs as much as $108,000, according to the company's website. LVMH's Bulgari sells one piece from its Divas' Dream collection, a diamond-filled flower-shaped ring with an emerald at the center, for $12,300, according to its website.

The pace of growth has been slower for Tiffany & Co., which, unlike its European counterparts, generates nearly half of its revenue from the Americas. The New York-based jewelry retailer's global sales advanced 2% year over year in the first half of 2017.

In China, women's self-purchasing represented 39% of nonbridal diamond jewelry sales in 2016, according to De Beers' research. Jewelry purchasing worldwide is getting a boost from the increasing wealth of middle classes in emerging economies. CM-CIC Market Solutions analyst Arnaud Cadart said in a telephone interview that he expects the women's market growth to continue "because you have more and more women that can afford to buy for themselves, notably in the emerging markets, especially China and Brazil."

Liz Chatelain, co-founder of luxury goods research firm MVI Marketing Ltd., in Austin, Texas, points to a phenomenon of self-purchases by a group of mature women with considerable income. She estimates that the average number of fine jewelry pieces bought per year by women between the ages of 35 and 55 over the past three years has edged up to 2.5 from two.

"There is this sweet spot: the 35 to 55 [year-old] women with a better income who are spending," Chatelain said in a telephone interview. "You're looking at the top 20% echelon in the market. They can afford the $1,000 to $4,000 fashion pieces just for them that are branded and real."

More buying power helps. In the U.S., women's earnings as a proportion of men's rose to 81% in 2015 from 62% in 1979, according to the U.S. Bureau of Labor Statistics.

However, prices for high-end items have gotten too high for some.

Yasuko Matsumoto, who bought Cartier, Bulgari and Tiffany pieces 20 years ago, said inflation in jewelry prices had put her off buying more, even though her salary as a clerk at a general trading house in Tokyo has doubled during that time. Matsumoto recently decided against replacing her Etoile band ring from Tiffany with a new one after discovering that the price for the same item had shot up.

"Looking at the prices now, I'm glad I took the plunge when I was younger and bought Bulgari, Cartier and other gemstone rings, even though they felt expensive at the time," Matsumoto told S&P Global Market Intelligence in an email.

As of Oct. 16, US$1 was equivalent to 111.69 Japanese yen.