If you guessed the Dow Jones or the S&P 500 index you are wrong. If you guessed it was Personal Savings Rate with the X-axis reversed, well done. The x-axis goes from last quarter to 1970.
Above is a 40 year of the S&P 500. You can compare it's look to all of the charts below.
Here is Personal Savings Rate unaltered
These last two graphs were lifted from Market Ticker (Hat tip Karl)