As of September 2011, Moody's Analytics has reinstated the "baseline scenario" ("_B") for the U.S. Macro Forecast.  This set of series has not been available for some time. The set's purpose is to preserve a baseline that corresponds to the "alternative scenarios" during the interval each month when the "current" forecast has been updated, but the alternatives have not yet been.

Why this timing?

First, understand that Moody's Analytics updates (runs) each of our forecast models once per month, using the latest values of the historical drivers.  The output is known as a "vintage."

For any given vintage, the baseline scenario is a copy of the current forecast -- but their vintages are not updated simultaneously.  Running the model and inspecting its output takes us several days, so we re-run with the alternative assumptions later, by about a week.  Consequently, each month exhibits an interregnum when the current and baseline forecasts (if you ignore the vintage) differ:

• Week 1: Current (January 2011), baseline (January 2011), alternatives (January 2011).
• Week 2: Current (February 2011), baseline (January 2011), alternatives (January 2011).
• Week 3: Current (February 2011), baseline (February 2011), alternatives (February 2011).

If you ran and downloaded a basket during week one or week three, FET.US = FET_B.US.  Whereas during week two, FET.US <> FET_B.US.  But at all times, you can be assured that the scenarios (FET_B.US versus FET_S1.US, FET_S2.US, etc.) were computed using comparable inputs and assumptions.

How to retrieve?

When using Data Buffet, you pick the current forecast, baseline scenario or alternative scenarios through the Geography Wizard in the forecast catalog. The dialog box shows a "Forecast Scenarios" panel with checkboxes, beneath the list of available geographies.  Each option is marked with its vintage date. (This panel does not appear in the historical catalog.)

When manually assembling a basket, the current, baseline and alternative series are differentiated by a suffix on the concept code: No suffix, _B and _S(number), respectively; e.g., FET.US, FET_B.US and FET_S1.US.

You can configure your basket output to include optional, supplemental metadata fields.  There is no metadata showing the forecast vintage, but you can show the "updated" and "last historical value" dates.