  Before the massive spread of computer technology, information was far from
complex. The development of technology shifted the paradigm: from individuals
who faced scarce and costly information to individuals who face massive amounts
of information accessible at low costs. Nowadays we are living in the era of
big data and investors deal every day with a huge flow of information. In the
spirit of the modern idea that economic agents have limited computational
capacity, we propose an original model using information overload to show how
too much information could cause financial markets to depart from the
traditional assumption of informational efficiency. We show that when
information tends to infinite, the efficient market hypothesis ceases to be
true. This happens also for lower levels of information, when the use of the
maximum amount of information is not optimal for investors. The present work
can be a stimulus to consider more realistic economic models and it can be
further deepened including other realistic features present in financial
markets, such as information asymmetry or noise in the transmission of
information.
