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How shorted was bluebird bio, Inc.? BLUE

bluebird bio, Inc. left the US market in 2025. This page is a frozen archive of its reported short interest, ending 31 Mar 2025. The ticker BLUE no longer refers to this company and may since have been reassigned.
18.15%
of shares outstanding reported short · settlement date 31 Mar 2025
vs previous report
−7.41
5 reports (~10 weeks)
−7.11
days to cover
2.58
Aggregate net short position time series for bluebird bio, Inc.

Markers along the chart's base: ▲ results announced (an 8-K reporting results was filed) ▲ quarterly or annual report filed. Dates are SEC filing dates; hover a point to see events since the previous settlement.

Days to cover

FINRA's own figure: reported shares short divided by the stock's average daily trading volume, published alongside each settlement. It expresses the short position in days of typical trading rather than as a percentage of the company; the two can move differently.

Aggregate net short position time series for bluebird bio, Inc. days to cover

Short interest around results

For each results announcement (an 8-K reporting results, by its SEC filing date), the FINRA settlement before it and the first one after. Settlements fall twice a month, so the two figures can sit up to a month apart and much else changes in between: this shows what was reported, not why.

Reported short interest before and after each results announcement
Results filedSettlement beforeSettlement afterChange
14 Nov 202424.60% 31 Oct 202422.51% 15 Nov 2024−2.09
9 May 202429.14% 30 Apr 202428.90% 15 May 2024−0.24
26 Mar 202431.13% 15 Mar 202427.21% 28 Mar 2024−3.92
8 Jan 202422.04% 29 Dec 202324.30% 12 Jan 2024+2.26
7 Nov 202322.97% 31 Oct 202320.57% 15 Nov 2023−2.40
8 Aug 202327.11% 31 Jul 202324.73% 15 Aug 2023−2.38
9 May 202322.14% 28 Apr 202322.08% 15 May 2023−0.06
29 Mar 202324.74% 15 Mar 202324.87% 31 Mar 2023+0.13
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Sector: Healthcare · By year: 2018 · 2019 · 2020 · 2021 · 2022 · 2023 · 2024

History

Full reported short interest history
Settlement dateShort %Change
31 Mar 202518.15%−7.41
29 Nov 202425.56%+3.05
15 Nov 202422.51%−2.09
31 Oct 202424.60%−0.88
15 Oct 202425.48%+0.22
30 Sep 202425.26%−2.88
15 Jul 202428.14%+0.05
28 Jun 202428.09%+1.13
14 Jun 202426.96%+0.32
31 May 202426.64%−2.26
15 May 202428.90%−0.24
30 Apr 202429.14%−0.69
15 Apr 202429.83%+2.62
28 Mar 202427.21%−3.92
15 Mar 202431.13%−0.09
29 Feb 202431.22%+5.07
15 Feb 202426.15%+1.00
31 Jan 202425.15%+0.85
12 Jan 202424.30%+2.26
29 Dec 202322.04%−1.26
15 Dec 202323.30%+3.31
30 Nov 202319.99%−0.58
15 Nov 202320.57%−2.40
31 Oct 202322.97%−0.09
13 Oct 202323.06%+0.52
29 Sep 202322.54%−4.61
15 Sep 202327.15%+2.80
31 Aug 202324.35%−0.38
15 Aug 202324.73%−2.38
31 Jul 202327.11%+3.26
14 Jul 202323.85%−6.52
30 Jun 202330.37%+1.75
15 Jun 202328.62%+5.36
31 May 202323.26%+1.18
15 May 202322.08%−0.06
28 Apr 202322.14%−0.18
14 Apr 202322.32%−2.55
31 Mar 202324.87%+0.13
15 Mar 202324.74%+2.69
28 Feb 202322.05%+1.15
15 Feb 202320.90%+0.04
31 Jan 202320.86%−1.40
13 Jan 202322.26%+0.26
30 Dec 202222.00%−0.26
15 Dec 202222.26%+0.22
30 Nov 202222.04%−1.20
15 Nov 202223.24%−5.99
31 Oct 202229.23%+0.13
14 Oct 202229.10%−0.35
30 Sep 202229.45%+3.39
15 Sep 202226.06%+0.46
31 Aug 202225.60%+4.25
15 Aug 202221.35%+0.09
29 Jul 202221.26%+2.49
15 Jul 202218.77%−2.35
30 Jun 202221.12%−3.40
15 Jun 202224.52%+6.88
31 May 202217.64%+0.32
13 May 202217.32%+0.31
29 Apr 202217.01%+1.05
14 Apr 202215.96%−0.11
31 Mar 202216.07%+4.89
15 Mar 202211.18%+0.94
28 Feb 202210.24%−0.01
15 Feb 202210.25%+0.33
31 Jan 20229.92%+0.09
14 Jan 20229.83%+1.57
31 Dec 20218.26%+0.34
15 Dec 20217.92%−0.26
30 Nov 20218.18%+0.48
15 Nov 20217.70%+0.15
29 Oct 20217.55%−0.97
15 Oct 20218.52%−0.02
30 Sep 20218.54%+0.81
15 Sep 20217.73%−0.72
31 Aug 20218.45%−0.90
13 Aug 20219.35%+0.08
30 Jul 20219.27%+0.57
15 Jul 20218.70%−0.69
30 Jun 20219.39%+1.46
15 Jun 20217.93%+0.36
28 May 20217.57%−1.17
14 May 20218.74%−0.67
30 Apr 20219.41%−0.59
15 Apr 202110.00%−0.22
31 Mar 202110.22%+2.07
15 Mar 20218.15%−1.40
26 Feb 20219.55%+0.38
12 Feb 20219.17%+0.21
29 Jan 20218.96%−0.30
15 Jan 20219.26%−1.61
31 Dec 202010.87%+0.39
15 Dec 202010.48%+0.17
30 Nov 202010.31%+0.02
13 Nov 202010.29%+0.74
30 Oct 20209.55%+0.27
15 Oct 20209.28%+0.04
30 Sep 20209.24%−0.07
15 Sep 20209.31%−1.03
31 Aug 202010.34%−0.04
14 Aug 202010.38%−0.22
31 Jul 202010.60%−1.93
15 Jul 202012.53%−0.68
30 Jun 202013.21%−0.36
15 Jun 202013.57%−0.08
29 May 202013.65%−0.14
15 May 202013.79%+0.45
30 Apr 202013.34%−0.31
15 Apr 202013.65%−0.12
31 Mar 202013.77%−0.14
13 Mar 202013.91%−0.53
28 Feb 202014.44%−0.16
14 Feb 202014.60%−0.46
31 Jan 202015.06%−0.40
15 Jan 202015.46%0.00
31 Dec 201915.46%−0.10
13 Dec 201915.56%+0.87
29 Nov 201914.69%−1.27
15 Nov 201915.96%+0.05
31 Oct 201915.91%−0.21
15 Oct 201916.12%−0.08
30 Sep 201916.20%+0.41
13 Sep 201915.79%+0.50
30 Aug 201915.29%+0.48
15 Aug 201914.81%+1.23
31 Jul 201913.58%+0.04
15 Jul 201913.54%−1.03
28 Jun 201914.57%+3.15
14 Jun 201911.42%+1.39
31 May 201910.03%+0.61
15 May 20199.42%+0.08
30 Apr 20199.34%−0.42
15 Apr 20199.76%+0.40
29 Mar 20199.36%−0.06
15 Mar 20199.42%−0.45
28 Feb 20199.87%+0.12
15 Feb 20199.75%+0.07
31 Jan 20199.68%+0.55
15 Jan 20199.13%−0.13
31 Dec 20189.26%+1.13
14 Dec 20188.13%−0.58
30 Nov 20188.71%−0.24
15 Nov 20188.95%+0.55
31 Oct 20188.40%−0.46
15 Oct 20188.86%+1.17
28 Sep 20187.69%−0.23
14 Sep 20187.92%+0.84
31 Aug 20187.08%−0.06
15 Aug 20187.14%−0.07
31 Jul 20187.21%+0.11
13 Jul 20187.10%−0.71
29 Jun 20187.81%+0.25
15 Jun 20187.56%+0.25
31 May 20187.31%+0.15
15 May 20187.16%−0.36
30 Apr 20187.52%−0.16
13 Apr 20187.68%+0.27
29 Mar 20187.41%−0.40
15 Mar 20187.81%+0.26
28 Feb 20187.55%−0.27
15 Feb 20187.82%+0.73
31 Jan 20187.09%+0.41
12 Jan 20186.68%−0.36
29 Dec 20177.04%–

Newest first. Scroll inside the table for earlier dates, back to 29 Dec 2017.

Frequently asked questions

How shorted was bluebird bio, Inc.?
bluebird bio, Inc. left the US market in 2025. Its final reported figure was 18.15% of shares outstanding for settlement date 31 Mar 2025, per FINRA's consolidated short interest report; this page preserves its full history.
What does this number include?
FINRA member firms must report their short positions in all US equities twice a month; FINRA consolidates them per security. We divide that official share count by the company's shares outstanding from its SEC filings. This is the regulatory figure, not a daily estimate.
Why does it only update twice a month?
US short interest is reported for settlement on the 15th and the last business day of each month, and FINRA publishes the consolidated figures about nine business days later. That cadence is set by regulation; no daily official figure exists.
Is this BLUE's short float?
No. This is short interest as a percentage of shares outstanding, the count in the company's SEC filings. "Short float" divides the same FINRA short count by the public float, which excludes closely held shares, so it comes out higher for the same company. We publish no float estimates: the float is not a regulatory figure.
What is BLUE's days to cover?
2.58 days for settlement date 31 Mar 2025: FINRA's own short interest ratio, the reported shares short divided by average daily trading volume. It is published in the same FINRA file and shown verbatim; we hold no volume data ourselves.
Which funds are short?
US public short interest is aggregate-only: individual short sellers are not named. Only some EU markets publish named positions.