When i was estimation a simultaneous equation model, a error massage appeared: You must include a constant in this sort of model.
Could anybody be kindly tell me the reason and how to solve the problem? Thanks!
PS. system setting:
# set the model up as a system
system name="all"
equation pf 0 gdpr pcr kaopen
equation pcr 0 pf gdp topen fdi efw
endog pf pcr
end system
# and estimate it in various ways
estimate "all" method=ols