The Citadel letter mentioned in the article (<a href="http:&#x2F;&#x2F;www.sec.gov&#x2F;comments&#x2F;10-222&#x2F;10222-16.pdf" rel="nofollow">http:&#x2F;&#x2F;www.sec.gov&#x2F;comments&#x2F;10-222&#x2F;10222-16.pdf</a>) is a very good read. I work in the industry and they hit all the main problems with IEX&#x27;s approach.