Macroeconomia Moderna: Lições e Desafios
Alex divulga um artigo interessante do Kocherlakota (via Mankiw), professor da Universidade de Minnesota e presidente do Fed de Minneapolis. O artigo é muito bom e aqui vão alguns comentários:
i) Curiosamente, bons economistas costumam beber da mesma fonte (ok, um pouco de pretensão. Só por eu leio o blog do Mankiw regularmente isto não me torna um bom economista. Mas saber que bons economistas como o Alex também o fazem, me faz me sentir membro de um clube especial....)
ii) Aos meus alunos de graduação de Tópicos Especiais de Macroeconomia (todos os dois): Kocherlakota enfatiza as cinco características essenciais da macroeconomia moderna, que já foram apresentados explicitamente nos modelos por nós discutidos:
" Modern macro models can be traced back to a revolution that began in the 1980s in response to a powerful critique authored by Robert Lucas (1976). The revolution has led to the use of models that share five key features:
- They specify budget constraints for households, technologies for firms, and resource constraints for the overall economy.
- They specify household preferences and firm objectives.
- They assume forward-looking behavior for firms and households.
- They include the shocks that firms and households face.
- They are models of the entire macroeconomy."
"Finally, just like old macro models, modern macro models are designed to be mathematical formalizations of the entire economy. This ambitious approach is frustrating for many outside the field. Many economists like verbal intuitions as a way to convey understanding. Verbal intuition can be helpful in understanding bits and pieces of macro models. However, it is almost always misleading about how they fit together. It is exactly the imprecision and incompleteness of verbal intuition that forces macroeconomists to include the entire economy in their models.
When these five ingredients are put together, the result is what are often termed dynamic stochastic general equilibrium (DSGE) macro models. Dynamic refers to the forward-looking behavior of households and firms. Stochastic refers to the inclusion of shocks. General refers to the inclusion of the entire economy. Finally, equilibrium refers to the inclusion of explicit constraints and objectives for the households and firms."
Os modelos DSGE são um pouquinho mais complicados, portanto é necessário ter um pouco mais de cuidado para "prever" a trajetória das variáveis endógenas do modelo como função das variáveis exógenas e dos choques que afetam a economia. Não dá para sair dizendo, como fazem os economistas de partido, que "se o governo gastar mais, ele estimula a demanda agregada e o produto e emprego cresce".
iii) Aos alunos do PPGE, curiosos com o recém inaugurado Núcleo de Pesquisa em Economia Computacional (batisado informalmente de "Nudepeecomputa" por algum gênio de marketing), sua relevância para macro é sintetizada pelo Kocherlakota:
"My own idiosyncratic view is that the division (between saltwater and freshwater economists) was a consequence of the limited computing technologies and techniques that were available in the 1980s. To solve a generic macro model, a vast array of time- and state-dependent quantities and prices must be computed. These quantities and prices interact in potentially complex ways, and so the problem can be quite daunting.
However, this complicated interaction simplifies greatly if the model is such that its implied quantities maximize a measure of social welfare. Given the primitive state of computational tools, most researchers could only solve models of this kind. But—almost coincidentally—in these models, all government interventions (including all forms of stabilization policy) are undesirable.
With the advent of better computers, better theory, and better programming, it is possible to solve a much wider class of modern macro models. As a result, the freshwater-saltwater divide has disappeared."Em suma, é parte importante do arsenal do macroeconomista moderno o domínio de softwares como Mathematica, Matlab, Maple, GAMs, Duali, etc. Obviamente, outras áreas da economia também se beneficiam destes avanços em teoria e em computação.
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