Someone commented that I've been "right on the money" with my remarks about investor sentiment at turning points this year. It wasn't me that was right. My intention isn't to play a game of right or wrong, but instead to have a clear view of that the market is telling me. When investor sentiment as measured by polls like the AAII Individual Investor Sentiment Survey is overly pessimistic after prices have already fallen, those who want to sell have already sold. That is, prices had already declined and then afterwards the investors state they are bearish (believing prices will fall) in the sentiment poll. It's an example of how people extrapolate the recent past linearly into the future. After prices have already declined we know there had been some selling pressure causing the downward price drift. That is, those who wanted to sell sold. If the new information was negative it was being priced in. Let's repeat that: when the news has been bad and prices have been falling the perceived bad news was being priced in. These things are always in the past. We can never speak of price trends and news in the future. If we are comparing a direction of price, we must always compare "now" to some point in time in the past. So, people are always experiencing the very recent past and tend to extrapolate it as if whatever happened recently will continue at that pace and direction.
Since I commented about the AAII Survey Shows Investors Bearish, Which is Bullish, which pointed out that individual investor sentiment was negative and that was positive, the stock indexes have gained about 4%. As the crowd suddenly turns afraid after prices have fallen, we know at least some of them have sold, so their fear is getting priced-in to the market as reflected by lower prices.
Now that prices have gained 4%, the AAII Individual Investor Sentiment Survey has turned optimistic again as evidenced by the graph below. After prices rise, they may be thinking "I need to make more money!” The problem is: THEY CAN'T BUY THE PAST. The only choice is now, or not now. We can do nothing in the past and we can do nothing in the future.

source: http://www.aaii.com/sentimentsurvey
The logical inconsistency here is that investors as a group tend to react to falling prices with fear and rising prices with greed. Note that my point here is in regard to the emotional reactions to rising and declining prices and how it relates to sentiment. That isn't to say a portfolio manager shouldn't sell as prices are falling. It isn't to say that a portfolio manager shouldn't buy as prices are rising, either.
Buying things that are rising and selling things that are declining is a proven strategy that is unmatched. It's the emotional extremes in sentiment that causes error. By the time the majority of people (and the media) sounds really pessimistic it's likely too late. They have a tendency to underreact or overreact. Their pessimism is already priced in. If you are getting your feelings from headlines your decisions will probably be far behind the curve. We could say the same about optimism. On April 27th I wrote that "Crowd Sentiment is Optimist: No Surprise to See at Least a Short Term Price Decline". Indeed, the stock indices went on to decline -17% and investor sentiment shifted from really optimistic to afraid and bearish as prices fell.
Keep in mind that we are speaking of emotions of fear and greed here. Investor sentiment can be thought of as a contrarian indicator: when the crowd turns bearish and prices have fallen, we know their pessimism is being priced in. Notice I qualified two things there: price had already fallen and investors were getting afraid and pessimistic about the future as they extrapolate what's happened recently into the future. Investor sentiment rarely turns negative before prices fall. In fact, the data shows investor sentiment is typically at a peak before major declines just as it was in April. The majority (the crowd) is constantly doing the wrong thing and the wrong time.
I am pointing out how emotional reactions relate to price changes primarily for the benefit for people to realize they are likely “one of them” whose sentiment may often be on the wrong side of the tape. However, know that most readers will say “Oh, not me” because of the tendency for overconfidence. The fact is, most people do poorly at portfolio management as evidenced by studies like this one by Dalbar. If most people create poor results and we are to create good results, we necessarily must be doing something very different than most people. A skilled portfolio manager with an edge will necessarily be be doing things very different that what you think should be done most of the time and that may include over long periods of time.
If investor sentiment is used as a contrary signal to "go the other direction" that's a countertrend signal. Countertrend methods are in conflict with trend-following signals. A countertrend method bets against a trend when it believes an extreme has been reached. A trend-following method rides with the direction of a trend until it changes. A trend-following system will remain positioned in the direction of the price drift until it changes and then it will exit or reverse to the other side. Therefore, a trend-following program will typically give up some of its profits in a position as the price reverses down in some magnitude before its exit point is reached. That is, no one ever knows the top, so you see the top after the fact when it’s reversed down. A countertrend method, such as using sentiment measures and indicators to define an extreme in investor sentiment as overly optimistic or overly bearish, would be contrarian signals for the portfolio manager. The portfolio manager may reduce exposure when the crowd is extremely optimistic or increase exposure to the potential for profit when the crowd appears overly pessimistic. The portfolio manager is basically selling to the crowd when they are willing to pay more and buying from them when the crowd is willing to sell for less. Of course, contrarian type countertrend methods sound good in theory, but they have their risks: even when sentiment is at an extreme it certainly doesn’t assure the opposite will occur immediately. That is why the execution of portfolio management requires skills and talents just as a surgeon, athlete, are business executive. But it's always about probability and mathmatical expectation, not certain outcomes. No investment strategy or portfolio manager can guarantee a profit or protect against loss.
You can probably see how complex decisions can be and why it takes a unique mental state along with vast research and testing to determine if various methods and parameters have a positive expected value (a good enough probability of creating the results that meet your objectives). For example, if a portfolio manager uses investor sentiment to reduce exposure when the crowd is extremely optimistic those things must be defined; what is extreme and how much exposure is reduced? These things can be quantified by quantitative data studies that test them as part of a complete portfolio management system. For me, when there is a directional drift I position capital in the direction of that trend and if it gets to an extreme as defined by several systems I have like sentiment, I may hedge or reduce exposure to the possibility of loss.