Performance attribution. Performance attribution is a process that tries to explain portfolio returns, namely by attributing parts of the return to explanatory factors. It's a process performed by the fund management company, investment consultants, or even asset owners, and it tries to slice and dice the achieved returns into several components. The traditional approach is often captured by the term Brinson Attribution, which decomposes returns based on portfolio weights versus benchmark. For example, it looks at whether or not the portfolio added value relative to the benchmark by choosing the right sectors or countries or by stock selection. Another method, so-called, Risk Factor Attribution, uses statistical analysis, such as regression analysis, to find out which underlying drivers, referred to as factors, explain the portfolio performance. Traditional factors include value, size, or momentum. While ESG metrics can be included in this analysis to learn whether or not fund returns relate to any ESG attributes of the portfolio holdings. There is an ongoing, active debate concerning what is an ESG factor and how it can be used in the attribution analysis. However, attribution in the ESG space remains a challenge. Fund managers sometimes solve this by providing a set of scenarios or case studies to clients detailing how they incorporated specific ESG issues into sector and security buy or sell decisions, and how these decisions have contributed to portfolio performance.