What Is Correlation?

Introduction

Correlation is a measure for how closely the market price of one ETF follows the market price of another. In our case, we always calculate how closely the market price of a given ETF follows the market price of SPY, an ETF that tracks the S&P 500. A correlation of 1.00 means that an ETF precisely tracks the movements of SPY. Similarly, a correlation of -1.00 means that an ETF precisely tracks the inverse movements of SPY.

Correlation is primarily a tool to build diversified portfolios for the long-term. Most people tend to prefer a stable portfolio that generates solid, consistent returns. It takes a portfolio of ETFs with different correlation levels to produce such a portfolio, as the markets go in cycles. Some years, the U.S. stock market performs well, while other years emerging market stocks perform well. Some years value stocks work well, while other years growth stocks work well. Also, ideally, if your portfolio includes some ETFs that are not closely correlated with SPY, your portfolio will perform better during the next market correction, as hopefully not everything in your portfolio will crash as much as SPY.

Our Calculations

Our calculations are done in the following manner:

• We calculate the correlation for each ETF over the entire lifetime of the ETF (from inception until today).
• Our calculations are automatically performed every night by our database, so all calculations are current (as of yesterday).

We use a SQL query on our Microsoft SQL Server database to generate the correlations.

Examples

Here are the correlations of some ETFs that we have chosen just to illustrate what different correlations look like.

SMDV's correlation to SPY is 0.8149

SPLV's correlation to SPY is 0.9714

USL's correlation to SPY is -0.4908

EEM's correlation to SPY is 0.5337

All data is a live query from our database. The wording was last updated: 01/25/2017.