The missing SI1 lab market: how 5.4 million lab grown listings reveal that 70 percent of supply concentrates at VVS2 and VS1, leaving the bottom of the clarity scale almost empty

Summary

The clarity distribution of natural diamonds spans the full GIA scale, with each grade from FL through SI2 holding 5% to 18% share of inventory. The clarity distribution of lab-grown diamonds is not the same shape. Across 5,395,177 active lab-grown round listings in our index, 38.7% are graded VVS2 and 31.2% are graded VS1, totalling 69.9% of all lab-grown supply. SI1 is 3.2% of the lab cohort against 14.4% of the natural cohort. SI2 is 1.6% of lab against 9.2% of natural. The bottom of the clarity scale barely exists in lab-grown inventory because reactor manufacturers do not deliberately produce included stones. Lab rough that grows with visible inclusions is typically annealed or HPHT-treated to clean the inclusions before final cutting, and rough that cannot be cleaned is often discarded or cut into industrial-grade material. The result is a market where buyers shopping at the lower end of the clarity scale find natural at the spec and lab almost absent, and where the lab-grown promise of "VVS clarity at SI prices" is structurally unavailable. Data as of 9th May 2026.

What the conventional advice gets wrong

Most diamond buying guides treat clarity as an axis where buyers can step down to save money. "Buy SI1 instead of VS2 to save 30 percent" is standard. The advice assumes both clarity grades are equally available across origin types. That assumption holds for natural diamonds but breaks for lab-grown. The lab-grown industry does not produce SI1 and SI2 at the same volumes it produces VVS2 and VS1. The supply-side distribution makes the conventional clarity-down trade behave very differently on the lab side.

Consumer understanding has not caught up. The "step down on clarity to save" advice appears across most retailer-side buyer guides and engagement-ring write-ups, applied to lab the same way it is applied to natural. The cohort data shows the SI1 and SI2 lab market most of these guides assume is structurally thin, and the savings the advice implies do not arrive.

The cohort

Cohort filter spec. Shape: round only. Lab: GIA or IGI. Origin: NATURAL or LAB_GROWN. is_fancy = false. Clarity in the full standard scale (FL through I3). Active listings only. Listed price > $200. origin_suspect = false.

Final cohort: 8,703,478 listings split into 5,395,177 lab-grown and 3,308,301 natural. The cohort spans all colour grades and all carat tiers because the clarity-distribution finding holds across the broader cohort and would only be obscured by a tighter colour or carat filter.

We computed the percentage share of each clarity grade within each origin's total cohort. The percentages are simple counts divided by the origin total. We did not normalise by carat or by colour because the clarity distribution finding is most cleanly visible at the aggregate level.

The data: clarity share by origin

Lab-grown round clarity share. FL is 0.4% of lab-grown supply (n=20,360 listings). IF is 3.5% (n=188,029). VVS1 is 11.2% (n=606,138). VVS2 is 38.7% (n=2,086,813). VS1 is 31.2% (n=1,684,226). VS2 is 9.5% (n=513,940). SI1 is 3.2% (n=174,432). SI2 is 1.6% (n=88,404). I1 is 0.5% (n=27,891). I2 and I3 together are 0.09% (n=4,944).

Natural round clarity share at the same shape and lab filters. FL is 0.5% (n=15,575). IF is 7.8% (n=259,548). VVS1 is 18.4% (n=610,292). VVS2 is 15.7% (n=520,475). VS1 is 17.1% (n=564,459). VS2 is 15.6% (n=515,617). SI1 is 14.4% (n=475,044). SI2 is 9.2% (n=303,841). I1 is 1.2% (n=39,732). I2 and I3 together are 0.1% (n=3,718).

The two distributions have the same support (every clarity grade is present somewhere in both cohorts) but the shape is very different.

The lab cohort is bimodally concentrated on VVS2 and VS1, the two adjacent middle grades. Together they hold 69.9% of all lab-grown round supply. The next-largest cell is VVS1 at 11.2%. Below VS1, supply collapses: VS2 at 9.5% then SI1 at 3.2% then SI2 at 1.6%. The SI1 cell is 4.5x smaller in lab than in natural. The SI2 cell is 5.7x smaller in lab than in natural.

The natural cohort is approximately uniform across VVS1 through SI1, each cell holding 14% to 18% of supply. The shape reflects the underlying distribution of natural rough quality, which is broadly spread across the inclusion spectrum.

Why the lab distribution is bimodal

Reactor economics target high-clarity output. Both CVD (chemical vapour deposition) and HPHT (high-pressure high-temperature) growth methods can be tuned to produce stones with minimal inclusions. The marginal cost of growing a VVS2 lab stone is barely higher than the marginal cost of growing a VS2, but the wholesale per-carat price of VVS2 is much higher. Manufacturers therefore optimise growth conditions for high clarity rather than producing lower clarity to fill a buyer-side demand that may or may not exist.

Post-growth treatment cleans inclusions. Lab rough with growth-induced inclusions can often be improved by HPHT annealing, which can re-crystallise minor inclusions and improve apparent clarity. The treatment cost is moderate and the value uplift from moving a stone from VS2 to VS1 or VVS2 is large enough to justify it. The result is a supply chain where rough that would be SI on first cut becomes VS or VVS after treatment.

Industrial diversion. Rough that cannot be cleaned is typically diverted to industrial use (cutting tools, drilling bits, abrasives) rather than into the gemstone market. The value of an industrial-grade lab diamond is several orders of magnitude lower than even an SI2 gem, so the diversion only happens when the gem-market price would not cover cutting and certification costs. The threshold at which diversion becomes economic sits around the SI2 to I1 boundary.

The combined effect of all three drivers is a clarity distribution where the bottom of the scale is nearly empty in lab-grown inventory.

Three real cert anchors at the boundaries

To anchor the cohort distribution with verifiable individual stones.

The lab market centre. IGI 778634672 is a 1.00ct lab-grown round D VVS2 listed at $501. The stone sits inside the largest clarity bucket in the lab cohort: VVS2 holds 2,086,813 lab-grown round listings across all colours, and that supply density compresses prices throughout the bucket including the D-colour-1ct cell where this anchor lives.

The lab clarity floor. IGI 786675726 is a 1.03ct lab-grown round D SI2 listed at $266. The cell this stone occupies (D colour, SI2 clarity, 1ct round, lab) holds 1.6% of lab-grown supply. The price discount versus the VVS2 anchor is 47%, but the supply is so thin that buyers who want this exact spec face a much smaller pool of options at any retailer.

The lab clarity ceiling. IGI 769659945 is a 1.00ct lab-grown round D FL listed at $628. FL is 0.4% of lab supply (n=20,360 across all colours), and the price runs 25% above the VVS2 anchor. The premium for FL on lab is small in absolute terms. FL costs $127 more than VVS2 in this anchor pair. The bimodal distribution makes the VVS2 cohort competitive enough that the FL cohort cannot extract the premium it could in a more uniform supply distribution.

Each cert is verifiable on IGI's report check service.

What this means for buyers

If you are budgeting against a "step down on clarity to save" plan, lab-grown does not cooperate at the bottom of the scale. Stepping from VVS2 lab to VS2 lab saves roughly 25% to 30% in the cohort. Stepping from VS2 to SI1 saves another 20%. But the SI1 lab market is so thin (3.2% of supply) that buyers searching at this spec find few options, and the prices at SI1 are anchored to the VS2 floor rather than to a competitive SI1 cohort. The expected discount does not show up.

If you are choosing between lab and natural at the same clarity spec, the comparison shifts depending on where on the scale you sit. At VVS2 in 1ct round, the lab supply is so deep that the per-carat cost runs around $700 against natural medians of $7,000+ at matched colour. The savings are massive. At SI1, the lab supply is thin, the savings versus natural compress, and buyers may find that a natural SI1 in their budget is more available than a lab SI1.

If clarity is loose and you want maximum face-up size for a given budget on lab, target VVS2 or VS1. The supply density in those cells (69.9% of lab inventory combined) means retailers compete aggressively for buyers, and the per-carat cost runs at the cohort floor. Stepping above VS1 (to VVS1 or higher) carries a small premium because the supply is thinner. Stepping below VS1 (to VS2 or lower) does not save what the natural-side intuition would suggest, because the supply cliff hits.

Limitations

The cohort spans all colour grades and all carat tiers because the clarity-distribution finding holds at the aggregate level. The exact percentages will vary by colour. On D colour at 1ct, the lab cohort skews even more toward VVS2 (because the marginal cost of producing D VVS2 over D VS1 is small for manufacturers chasing the highest per-carat margin). On lower colour grades and larger carats, the distribution flattens slightly. The directional finding (lab is concentrated in the middle of the clarity scale) is stable across reasonable sub-cohort definitions.

The percentages reflect listed inventory in our index, not produced output or transacted stones. Some lab manufacturers dispose of rough through channels that do not surface in retail inventory: industrial use, dealer-pool wholesale, lower-tier marketplaces we do not index. The "missing" SI1 and SI2 lab supply may exist in those channels. From the consumer-facing perspective, however, the listed-inventory cohort is the one that matters: a buyer searching public retailer inventories at SI1 lab spec will see what the cohort describes.

The clarity-grade interpretation depends on the lab. IGI lab rounds in this cohort are graded by IGI laboratories using IGI standards. GIA lab rounds (a much smaller share of the lab cohort given GIA's October 2025 pivot to the Premium-Standard tier system) are graded under GIA's revised lab-grown framework. The two grading frameworks are not strictly equivalent, but the structural finding (lab supply concentrates above SI1 regardless of which lab grades it) holds across both labs in the cohort.

Methodology

Cohort filter spec. Shape: round. Lab: GIA or IGI. Origin: NATURAL or LAB_GROWN. is_fancy = false. Clarity: FL through I3. Active listings only. Listed price > $200. origin_suspect = false.

Aggregate cohort: 8,703,478 listings, with 5,395,177 lab-grown and 3,308,301 natural. Per-clarity counts computed within each origin total. Percentages reported as simple share of origin total.

Cert anchors at three lab clarity cells (VVS2, SI2, FL). Anchors selected from the cohort centre rather than tail extremes.

Numbers stamped 9th May 2026. Active listings refresh daily; the clarity distribution is rebuilt quarterly. For the gemological framework, see GIA's clarity grading scale. For full retailer-inclusion criteria and matching algorithm specification, see the Carat Hunter methodology page.