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 ONCE'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 ONCE's days to cover?

7.64 days for settlement date 13 Dec 2019: 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.

How shorted was Spark Therapeutics, Inc.? ONCE

Spark Therapeutics, Inc. left the US market in 2019. This page is a frozen archive of its reported short interest, ending 13 Dec 2019. The ticker ONCE no longer refers to this company and may since have been reassigned.

9.11%

of shares outstanding reported short · settlement date 13 Dec 2019

vs previous report: +0.10
5 reports (~10 weeks): −0.59
days to cover: 7.64

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.

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 filed	Settlement before	Settlement after	Change
19 Feb 2019	15.29% 15 Feb 2019	6.59% 28 Feb 2019	−8.70
7 Jan 2019	12.95% 31 Dec 2018	13.45% 15 Jan 2019	+0.50
6 Nov 2018	14.46% 31 Oct 2018	14.44% 15 Nov 2018	−0.02
7 Aug 2018	13.96% 31 Jul 2018	14.65% 15 Aug 2018	+0.69
8 May 2018	13.04% 30 Apr 2018	13.62% 15 May 2018	+0.58
20 Feb 2018	12.68% 15 Feb 2018	12.45% 28 Feb 2018	−0.23
9 Jan 2018	13.06% 29 Dec 2017	12.69% 12 Jan 2018	−0.37

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Paste this snippet to embed the interactive chart. It updates with each FINRA report and keeps the source attribution. Preview

<iframe src="https://howshorted.com/embed/us/once-2020/" width="100%" height="430" style="border:0" loading="lazy" title="Spark Therapeutics, Inc. short interest chart"></iframe>
<p>Source: FINRA data compiled by <a href="https://howshorted.com/us/company/once-2020/">howshorted.com</a></p>

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Plain

Short position data for Spark Therapeutics, Inc.: FINRA, compiled by howshorted.com, settlement date 13 Dec 2019. https://howshorted.com/us/company/once-2020/

Wikipedia

<ref>{{cite web |title=Spark Therapeutics, Inc. short position data |url=https://howshorted.com/us/company/once-2020/ |website=HowShorted |publisher=howshorted.com (data: FINRA) |date=2019-12-13 |access-date=2026-10-13}}</ref>

BibTeX

@misc{howshorted-spark-therapeutics-inc-2019-12-13,
  title        = {Spark Therapeutics, Inc. short position data},
  author       = {{HowShorted}},
  howpublished = {\url{https://howshorted.com/us/company/once-2020/}},
  note         = {Data: FINRA, settlement date 13 Dec 2019; accessed 2026-10-13},
  year         = {2019}
}

Sector: Healthcare

History

Full reported short interest history
Settlement date	Short %	Change
13 Dec 2019	9.11%	+0.10
29 Nov 2019	9.01%	−0.17
15 Nov 2019	9.18%	−0.01
31 Oct 2019	9.19%	−1.31
15 Oct 2019	10.50%	+0.80
30 Sep 2019	9.70%	+1.16
13 Sep 2019	8.54%	+0.48
30 Aug 2019	8.06%	+0.37
15 Aug 2019	7.69%	+0.39
31 Jul 2019	7.30%	−1.08
15 Jul 2019	8.38%	+0.31
28 Jun 2019	8.07%	+1.99
14 Jun 2019	6.08%	+0.24
31 May 2019	5.84%	+0.20
15 May 2019	5.64%	+0.84
30 Apr 2019	4.80%	−0.72
15 Apr 2019	5.52%	−0.25
29 Mar 2019	5.77%	−1.03
15 Mar 2019	6.80%	+0.21
28 Feb 2019	6.59%	−8.70
15 Feb 2019	15.29%	+1.25
31 Jan 2019	14.04%	+0.59
15 Jan 2019	13.45%	+0.50
31 Dec 2018	12.95%	+0.12
14 Dec 2018	12.83%	−0.75
30 Nov 2018	13.58%	−0.86
15 Nov 2018	14.44%	−0.02
31 Oct 2018	14.46%	−0.78
15 Oct 2018	15.24%	−0.34
28 Sep 2018	15.58%	+0.21
14 Sep 2018	15.37%	+0.60
31 Aug 2018	14.77%	+0.12
15 Aug 2018	14.65%	+0.69
31 Jul 2018	13.96%	−0.33
13 Jul 2018	14.29%	−0.24
29 Jun 2018	14.53%	−1.78
15 Jun 2018	16.31%	+2.18
31 May 2018	14.13%	+0.51
15 May 2018	13.62%	+0.58
30 Apr 2018	13.04%	−1.18
13 Apr 2018	14.22%	+0.82
29 Mar 2018	13.40%	−0.51
15 Mar 2018	13.91%	+1.46
28 Feb 2018	12.45%	−0.23
15 Feb 2018	12.68%	−0.71
31 Jan 2018	13.39%	+0.70
12 Jan 2018	12.69%	−0.37
29 Dec 2017	13.06%	–

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

Frequently asked questions

How shorted was Spark Therapeutics, Inc.?: Spark Therapeutics, Inc. left the US market in 2019. Its final reported figure was 9.11% of shares outstanding for settlement date 13 Dec 2019, 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 ONCE'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 ONCE's days to cover?: 7.64 days for settlement date 13 Dec 2019: 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.