Approximately every 7.75 months the stock hits it's lowest point. However, this low point is on an upward trend. If you can estimate when it has hit it's low point, you will see a drastic increase shortly after.
We're a seeing a 4 month low for ACM. At this point, we've seen this stock rise and fall pretty regularly. If you're looking for a short term gain, I'd say this is a good option. I think it'll hit a 2 month high within these next 1-2 weeks.