The IPI is an indicator prepared by the Board using data from the Bureau of Labor and Statistics to measure the total output from several key industrial production industries: Manufacturing, Mining, Electricity, and Gas specifically.
The reason why I found this chart interesting is twofold. One, although I would not use it as a rote timing indicator, the tendency for the past several decades is that high industrial production is reflected by positive market returns on a long-term timeframe.
Two, and more topically, a popular meme in the financial media is that industrial production in America is weak, and this shows that not only is the absolute level of output making a new high, but the YoY is also accelerating over prior months.
The most recent YoY value of 6.077% is the highest reading since February 2011.