# Disentangling Structural Breaks in Factor Models for Macroeconomic Data

## TL;DR

This paper introduces a projection-based method to distinguish between breaks in factor variance and loadings in macroeconomic data, revealing that the Great Moderation was primarily a variance reduction.

## Contribution

It develops a novel decomposition technique that separates structural breaks in factor variance from loadings, improving analysis of macroeconomic structural changes.

## Key findings

- The Great Moderation is mainly a break in factor variance, not loadings.
- Over 70% reduction in total factor variance during the Great Moderation.
- Standard methods conflate breaks in variance and loadings, leading to misinterpretation.

## Abstract

We develop a projection-based decomposition to disentangle structural breaks in the factor variance and factor loadings. Our approach yields test statistics that can be compared against standard distributions commonly used in the structural break literature. Because standard methods for estimating factor models in macroeconomics normalize the factor variance, they do not distinguish between breaks of the factor variance and factor loadings. Applying our procedure to U.S. macroeconomic data, we find that the Great Moderation is more naturally accommodated as a break in the factor variance as opposed to a break in the factor loadings, in contrast to extant procedures which do not tell the two apart and thus interpret the Great Moderation as a structural break in the factor loadings. Through our projection-based decomposition, we estimate that the Great Moderation is associated with an over 70\% reduction in the total factor variance, highlighting the relevance of disentangling breaks in the factor structure.