One of the most popular tools for identifying how tired a market (SPY) move is getting is the cumulative advance decline line.
The NYSE cumulative advance decline line is a simple calculation, which adds the difference between the current day's advancers and decliners to the previous days reading. By doing this, it gives insight into whether the move higher or lower is lifting all boats, or just a select few.
When the line diverges from the market's price action, its often a signal to head for the sidelines. As you can see from the following chart, the NYSE cumulative advance decline line has been trending up since early June.
You'll also notice it peaked near the start of both April and May. Will it peak near these levels again in July?
So far, it hasn't rolled over. But, you should keep a close eye on the measure because it may serve as an early warning signal investors aren't as willing to embrace risk as we march into prior resistance near Dow 13,000.
Disclosure: I have no positions in any stocks mentioned, and no plans to initiate any positions within the next 72 hours.