Aggregation

Heterogenität ist essentiell für die Modellierung von Konjunkturzyklen sagen Sungbae An, Yongsung Chang and Sun-Bin Kim (via Economic Logic):

Accounting for observed fluctuations in aggregate employment, consumption, and
real wage using the optimality conditions of a representative household often
requires preferences that are incompatible with economic priors (e.g., Mankiw,
Rotemberg, and Summers 1985). This discrepancy between the equilibrium model
and the aggregate data is often viewed as evidence of the failure of labor-market
clearing. We argue that such a conclusion is premature. We construct a model
economy where all prices are flexible and all markets clear at all times but house-
hold decisions are not readily aggregated because of incomplete capital markets
and the indivisible nature of the labor supply. We demonstrate that if we were to
explain the model-generated aggregate time series using decisions of a "fictitious"
stand-in household, such a household is likely to have a non-concave or unstable
utility. Our analysis suggests that the representative-agent model often fails to
represent an equilibrium outcome of a heterogeneous-agent economy.

Das erklärt warum Schätzungen mit aggregierten Daten of zu anderen Ergebnissen kommen als Schätzungen mit disaggregierten Daten, so z.B. in Schätzungen zur Elastizität der Arbeitsangebotselastizität, die für Konjunkturmodelle sehr wichtig ist:

micro-estimates using household or payroll data indicate that the elasticity is about 0.1: a 10% increase in wages would increase the labor supply by 1%. Using aggregate data, macro-estimates obtain an elasticity around 1, an order of magnitude higher.