Hundreds of indexes are available today for measuring trends in and performance of financial markets. This development reflects the role technology tools has played in the breadth of available indexes. Exchange-traded indexes provided a ready market for new investment ideas. It no longer is the case that just one index is presented as representative of large and/or closely followed markets or market sectors. Most market participants are well-aware of the longstanding indexes of broadest interest that track markets and sector. At the same time, understanding of the nuances of market index construction and the implications across market environments likely varies widely. The perspective here provides some thoughts on market indexes, their construction and use, with implications for financial markets and portfolio construction.