the overall expected/projected yields

The underlying outlook > the present but not readily noticeable future prospect is good / healthy. Underlying > hidden but can be noticed /real but not ​immediately ​obvious ( they are a few other meanings for this word ) I can see his underlying guilt by the way he behaves. Outlook> prospect/expectation for the future .> What is your outlook for this year in terms of investing in shares?

It must refer to the economic perspective, whatever the context, bonds, for example.