What Asset Classes are used for Returns in the 1800s or early 1900s?

When using historical sequences of returns, the software uses specific asset-class returns when available. However, when going further back in history, more general asset class returns are used when necessary. For example, before mid-cap value returns are available as a separate set of asset-class returns, the system uses mid-cap blend returns. Before mid-cap blend returns are available, the software uses all-cap or large-cap returns.

In summary, at each point in history, the most specific available returns are used. Further back in history, more general returns are used.