Presumably any ETF is tracking something, that you could define to be an "index"...

lmm on March 8, 2016 | parent | context | favorite | on: The ETF Files: How the U.S. government inadvertent...

Presumably any ETF is tracking something, that you could define to be an "index" in a degenerate sense (even if it's the "companies Buffet thinks are undervalued index", or the "solid gold bars index"). Or is there a technical definition of index?