The MO (McClellan Oscillator) is an indicator of future market movements related to the number of advancing or declining securities on the NYSE, as opposed to the average price change. The McClellan Oscillator is calculated by taking a 19-day exponential moving average (EMA) of the net number of securities that are advancing and subtracting a 39-day EMA of the same thing.
That is, the McClellan Oscillator is expressed as:
Oscillator = (19-day EMA of securities advancing - securities declining) - (39-day EMA of securities advancing - securities declining).
The importance of the McClellan Oscillator comes from the fact that price averages may be driven by only a few securities. That is, a few securities may be making large gains while the rest of the securities on the NYSE are posting losses, or vice versa. A price average, then, may not reflect the true conditions of the market. The McClellan Oscillator attempts to control this.
Having said that, my point is:
The S&P or the Dow are not indicative of the true market situation. The market is far more oversold and bearish than is being conveyed via popular market indicators. The Basic Materials sector (more than any other sector) is really in tune with the true state of the market. Other sectors (Financial, Technology) will soon follow. There is nothing wrong with ACI fundamentally, nor is Obama trying to ruin the coal industry :). Just be patient while the momentum turns the other way from oversold and until the summation index crosses the 0 line. It will soon.