While their methodologies and results vary to some extent, even a cursory glance at the major diamond price indexes (RapNet, IDEX, Mercury, PolishedPrices) reveal an undeniable trend of continuing and sustained polished price declines. This conclusion is drawn notwithstanding the weekly market reports, all of which concur that the diamond market is entering the yearly quiet period, with the start of the summer holidays in the US and Europe slowing trade there and in their related markets, such as India and Israel. The real concern, however, is not the cyclical slowdown, but sluggish prices. As Ehud Laniado, principal at Mercury Diamond writes, referencing their Global Price Tracker, "This is the 31st consecutive month that the index is declining year-over-year. During the 31 month period, the index declined 11.6%, underscoring the continued softness of the polished diamond market."
Laniado detects a higher rate of decline in June prices than is typically seen following major trade shows JCK Las Vegas and Hong Kong Jewellery Show, which is "worrying". Rapaport News agrees, recently writing, "Polished diamond prices softened in June after the JCK Las Vegas show demonstrated a cautious and changing US market", while Laniado writes, "Historically, prices tend to rise in June because of the shows, which didn’t happen. We are concerned that the growth in the rate of decline indicates a certain disappointment on the part of polished diamond wholesalers in the level of demand, and their response to that low level of demand. The greater implication of the ongoing price decline is the erosion in consumer demand." This seems to corroborate what the index shows, namely, "The polished price decline trend started in December 2014, and has been running continuously since then."
The indexes generally show (not a consensus) that the smallest goods (0.30 carats) are the only ones consistently performing well right now, with prices of larger goods (from 0.50 to 1.0 carats) typically down 5% - 10% for the year. Laniado writes, "The year-over-year overall decline in prices is comprised of smaller components, namely the individual performance of a wide range of goods. It is therefore no surprise that on a year-over-year basis, every size range declined in price, many in the mid-single digits." He concludes, "The long-term overall weakness in polished diamond prices is an ongoing issue, and despite our cautious optimism following the May results, the price outcome in June paints a negative and gloomy picture of the market. We are especially concerned that the month-over-month declines during June were even deeper than those that took place during May, because it shows that even the trade shows, designed to give a boost to business, have not succeeded in generating enthusiasm." As he - along with everyone else in the industry - emphasizes, "The ongoing decline in prices, and the decline in consumer demand that it reflects, is not a one-way street. For some time, we have been urging the diamond industry to invest in marketing in order to drive consumer demand."