First, there is all kinds of economists from every political view that exist.

The point people don't understand is that is not about economists know or don't know what will happen.

The main tool an economist use is the analysis of data and translating it to statistics. If done the right way, these statistics show the probability of a certain event to happen.

But the problem with statistics is that the data may be manipulated to reach a specific results.

In that way, most of the Economist report/predictions is biased by the Economist personal views (political or economic), so to actually analyse and understand what an economist is saying, you need to understand were that economist stand on political and economic matters.

In the end, Economist opinions is a bet based on the probability/accuracy of the data they chose to use to analyze the problem.