In the last chapter we illustrated the dilemma that we face when we use centred averages as proxies for trends. We have a gap of half of the period of the average during which we do not know what the average (trend) has been doing. Before we can begin to think about the future movement of the trend we have to examine ways in which we can make a decent estimate of its current position.
Figure 9.12 from the last chapter is presented again here as Figure 10.1 in order to focus on what is required. The average is known up to the point where it divides into three possible paths.