Strange sign reversal of simulated series in stochastic simulation

[jpfeifer]

See e.g.

Parameter drift with parameters' bounds

What is the reference for what you are trying to do? In general, if you work with a log-linear approximation, there is not way to bound variables (like your capital share) due to linearity. One has to live with this and hope that the data do not assign much probability to it violating the theoretical bounds.