Text and Data Mining valid from 2020-02-05
Received: 5 November 2018
Accepted: 15 December 2019
First Online: 5 February 2020
Change Date: 24 March 2020
Change Type: Correction
Change Details: After publication of this article , it is reported this article contained an error in the section ‘Risk-free return (rf)’
: The author declare that he or she has no competing interests.