What do economists mean when they say markets are efficient

What do economists mean when they say markets are efficient

What do economists mean when they say markets are ‘efficient’? Are global markets efficient?

Must be APA format 800 words. Must include the references below.

Chauhan, Y., Chaturvedula, C., & Iyer, V. (2014). Insider trading, market efficiency, and regulation. A literature review. Review of Finance & Banking, 6(1), 7-14.

Klock, S. A., & Bacon, F. W. (2014). The January effect: A test of market efficiency. Journal of Business & Behavioral Sciences, 26(3), 32-42.