Empirical Data on Refactoring?

Question

Are there any empirical studies that show the impact of refactoring (or lack of refactoring) on a development team's productivity?

(NOTE: I'm only looking for empirical data--From my own experience, I personally know that refactoring works, but I was wondering if there was some hard data to back that claim).

Answer 1

Trends in Java code changes: the key to identification of refactorings?

A Case Study on the Impact of Refactoring on Quality and Productivity in an Agile Team

Extracting refactoring trends from open-source software and a possible solution to the 'related refactoring' conundrum

The Effectiveness of Refactoring, Based on a Compatibility Testing Taxonomy and a Dependency Graph

And lastly

Answer 2

This article looks to have the info you seek.