Biogen Inc.

Where the centre comes from

The middle of the band is our expected return for this asset over the next year. We start from what investors as a whole can expect to earn and share it out across asset classes, sectors and companies, in proportion to how much risk each carries and how they move together. Where we have specific information — analysts raising or cutting their earnings forecasts, for example — we move a company’s expected return up or down, and say why beneath the chart. The middle line is the typical outcome rather than the average, so the more volatile the asset, the further below its expected return it can sit.

How the paths are drawn

Each path is one possible year, drawn many times over. It starts at today’s price and drifts toward the expected return above, while its day-to-day swings are as large as this asset’s own swings over the past few years — its historical volatility. Repeating that thousands of times gives thousands of different years. The band is the range most of them passed through, and the bell curve is how they were spread out at year end.