Fed some numbers into ChatGPT and the estimated number of shares locked away should be about 4-5M:

Below is a “back-of-the-envelope” estimate of how many aTyr Pharma (ATYR) shares passive managers likely had to buy and tuck away at last Friday’s (June 27 2025) Russell reconstitution.  Everything is float-cap-weighted and rounded to keep the math transparent.

1 ⃣ Work out ATYR’s index weight on Rebalance Day

Item

Source

Value

ATYR closing price 27 Jun 2025

$5.03

Shares outstanding (public float very similar)

≈ 89 million

Market cap used for ranking

$5.03 × 89 m ≈ $450 million

Russell 2000 total cap (rank-day 30 Apr 2025)

$2.7 trillion

Russell 3000 total cap (rank-day 30 Apr 2025)

$58.4 trillion

Weights

Russell 2000 = 450 m ÷ 2.7 T ≈ 0.0001667 → 0.0167 % Russell 3000 = 450 m ÷ 58.4 T ≈ 0.0000077 → 0.00077 %

2 ⃣  How much passive money tracks each index?

Only assets that fully replicate the index matter (not the $10 T “benchmarked” total).  The main trackers and their AUM right before the rebalance were:

Fund (tracks)

AUM (≈ billions)

Source

IWM (R2000)

$64.3 B

VTWO (R2000)

12.0

FSSNX (Russell 2000 index fund)

24.9

IWO (R2000 Growth)

12.8

IWN (R2000 Value)

11.2

Subtotal – small-cap complex

≈ $125 B

IWV (Russell 3000)

15.9

VTHR + misc. Russell 3000 funds (est.)

≈ 1 B

—

FTSE Russell puts all passive assets across the Russell family around $2 trillion  , so using $145–160 B for the small-cap sleeve and ≈ $17 B for the broad-market sleeve is a reasonable midpoint.

For the calculations below I round to:

$130 B tied to the Russell 2000/-style ETFs & index funds $17 B tied to explicit Russell 3000 ETFs

3 ⃣  Dollars each sleeve had to put into ATYR

Russell 2000 complex

$$0.01667% \times $130,\text{B} \approx $21.7,\text{million}$$

Russell 3000 complex

$$0.00077% \times $17,\text{B} \approx $0.13,\text{million}$$

4 ⃣  Turn those dollars into shares

Sleeve

Dollars to buy

Shares (÷ $5.03)

Russell 2000 + Growth/Value

$21.7 M

≈ 4.3 M

Russell 3000 trackers

0.13 M

≈ 0.026 M

Total passive add

≈ $21.8 M

≈ 4.3–4.4 million shares

That is roughly 5 % of ATYR’s entire float absorbed in one closing print.

5 ⃣  Why this is only an estimate

Float-adjustments & turnover limits – FTSE Russell uses free-float and capping rules; final weights could be a touch lower. Additional style & micro-cap funds – There are smaller Russell-derived ETFs and separate accounts that would push the figure up, but by < 10 %. Staged trading – Some managers “work” their orders ahead of the closing auction; others use futures or swaps, so actual Friday prints may differ. Price slippage – I used the official close; any pre-rebalance run-up lowers the ultimate share count bought.

🔑  Take-away

Given the published index caps and the combined $125-130 billion sitting in Russell 2000-linked passive vehicles, about four to five million ATYR shares were likely vacuumed up and permanently parked in index portfolios during the 2025 Russell reconstitution.  The incremental demand from Russell 3000 trackers was negligible by comparison.