Dear all,

I would like to replicate a paper (https://onlinelibrary.wiley.com/doi/10.1002/smj.3057) that uses an unconditional HLM model to decompose variation in firm performance. Firm performance is observed over time. Particularly, the authors write:

"We used a 4-level nested HLM model of years (level 1), nested within board chairs and CEOs (level 2), nested within firms (level 3), which is finally nested within industries (level 4). It should be noted that both the board chair effect and CEO effect are at the same level of analysis (level 2), as there is not a nested relationship between these two effects. Following the terminology used by Bryk and Raudenbush (1992), we used level 1 to denote the lowest level, and level 4 to denote the highest level. In the HLM analysis, we followed Singer’s (1998) guidelines and selected the “unstructured” covariance structure."

If there is only CEO (level 2) or board chair (level 2), then the model seems intuitive to estimate using the -mixed- command, i.e.,
Code:
mixed performance || industry: || firm: || ceo:
However, I am not sure how to enter both board chair and CEO that are both on the same level and calculate the proportion of each respective variance.

Would be grateful for your help.