I have some misgivings about the field of econometrics, fundamental elements are missing, and traditionally even if GMM estimation, is within the realm of admissable methods in statistics, it is quite fringe. This is also true of MA, ARMA and ARIMA for me, because in the case of economics they are not backed by fundamentals, nor do they elucidate them, given a theoretical mismatched. This is on some level, the same misgivings I have for Robert Lucas Jr.'s attempt to bridge micro to macro, through the use of statistical methods. There is some intuition or concept gap, where certain things are not being bridged. At least from what limited I have read. Perhaps, this is worthy of some further exploration.