For those of you who have inquired, the "Yi" is my own proprietary overbought/oversold indicator. A +10 reading generally indicates we are overbought in the overall market, and -4 or a -5 reading is telling us the market is a bit oversold. The "zero line" in between the plus and minus readings will sometimes act as an area of support or resistance, so I tend to keep an eye on that level also. A reading of +20 is extremely overbought, and a -10 indicates the market is extremely oversold.