Challenges in calculating portfolio metrics. Integrating ESG factors into security analysis, portfolio construction, and measuring portfolio metrics poses a range of challenges, which particularly include lack of data, issues with data quality, as well as data consistency. Many companies simply do not report much data. When it is reported, it may not be reported in a consistent way. Also, most ESG data is not audited, and therefore in many scenarios, the analysts use data that is reliant on judgments made by others. When it comes to carbon emissions disclosures, the data may be incomplete, particularly if the analyst is looking for total carbon emissions. The issue here is that most companies normally report scope 1 and scope 2 emissions, which are the emissions which are most attributable to the company, but disclosure on scope 3 emissions are sparse. As a separate example, imagine that you try to calculate portfolio ES and geometrics for a particular fund. The data availability challenge comes from the fact that while a large amount of ESG data exists and is available, it may not be available for some of the stocks that a portfolio holds. For example, if a fund management group uses data provided by one of the ESG ratings agencies, the data may cover 80% or even 90% of the securities held, but not the remaining 20% or 10%, presenting a coverage gap. A solution then has to be found. One such solution takes the form of rescaling the scoreable portion to 100% by proportionally resizing each scoreable position. This is possible if the coverage gap is not too excessive.