Daily

My father wrote a poem in Korean and called it 참회(懺悔), ‘Repentance.’ The full poem, followed by my short response.

The structure of walk-forward analysis, the metrics it produces (IS-OOS gap, parameter stability), a momentum-lookback tuning case, and the limits that keep it from being a universal validator.

The core constraints of the four Korean retail account types — general, ISA, pension savings, and IRP — covering tax-free thresholds, tax deductions, the 70% risk-asset cap, and access to direct foreign investment, plus a strategy-to-account mapping.

Concrete cases of look-ahead bias and survivorship bias — full-period momentum normalization, financial disclosure lag, close-on-close fills, S&P 500 reconstitution, the limits of free APIs — followed by an avoidance checklist.

Covers Markowitz’s mean-variance model as the mathematical foundation for setting asset weights, the two optimal points on the efficient frontier (Min-Variance and Tangency), and the practical adjustments that compensate for the model’s weaknesses.

Covers technical indicators (RSI, SMA Cross, MACD, Bollinger Bands) for reading price movements, composite signal design, and a comparison of three strategy types across different time horizons.

Covers factor scoring methods (Z-Score, Rank) for combining indicators into a single score, plus the basics of rebalancing and asset allocation.

Covers the formulas and interpretation of CAGR, MDD, Sharpe Ratio, and other backtest metrics, plus five common backtesting pitfalls.

Covers the role of price momentum and dividend yield as factors in quant investing.

Covers how to judge whether a company is cheap (valuation) and whether it earns well (quality) — formulas and interpretation of PER, PBR, PSR, ROE, ROA, and debt ratio.