This report from FINRA is misleading.  This report shows half or more of the volume sold short on mnay days for many stocks.  Most of these "shorts" are covered later in the day by the MM's.  Actual short volume is much less.  From another board:

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"This is what FINRA, the exact same source which you used to post the #, said.

"Thank you for contacting FINRA’s Office of the Ombudsman. Regarding your question, it would be incorrect to assume that short sales comprise 32% of the total volume on that trading day for IPIX. FINRA publishes the daily short sale volume pursuant to an SEC mandate; however, there are various trading anomalies that result in the reported short sale volume often being exaggerated. Thus, the true total short sales volume may be significantly lower than the volume that is reported. Third parties sometimes ignore this and try to claim the ratio is valid to further their own objectives.""

MMs mark shares short temporarily to execute trades and they are almost always covered in the same day, therefore the actual short % is much lower than the # suggests.
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