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Technical Notice

FINRA Appendix B.I Data from April, 2016 through September, 2017 Contains Errors

August 28, 2019

Due to errors in the underlying reference data, FINRA Appendix B.1 data incorrectly excluded certain orders from the monthly order counts during the period spanning April, 2016 through September, 2017.  As a result of this under-representation, the corresponding average calculations for four trading centers across as many groups were also impacted.  The aggregate monthly maximum impact of this under-representation across all impacted months involved is approximately 2.7% of all orders included in FINRA Appendix B.I data.  FINRA does not intend to re-publish this data.