Hi David, thanks for your thoughtful questions. The analysis used long-short factors for explaining and then replicating the performance of BRK using these as building blocks. The factors are constructed via well-diversified portfolios of liquid US stocks and are not particular capacity constrained. The factor mimicking portfolio doesn't have a high turnover and we included transaction costs. The objective of the analysis was simply aimed to see if factors explain the outperformance of BRK, which they do.