Finance articles from Pickuma. Tested, not generated.https://pickuma.com/en-ushttps://pickuma.com/posts/backtest-data-biases-that-ruin-equity-research/https://pickuma.com/posts/backtest-data-biases-that-ruin-equity-research/Survivorship bias, look-ahead bias, point-in-time data, and the rest of the subtle ways your beautiful backtest is overstating returns. With concrete fixes for each.Tue, 19 May 2026 00:00:00 GMTfinanceOwenhttps://pickuma.com/posts/boring-math-of-compound-returns/https://pickuma.com/posts/boring-math-of-compound-returns/Compound interest sounds like magic. The math is mundane and the most common rules of thumb are subtly wrong. Here's a calmer take on what compounding actually delivers.Tue, 19 May 2026 00:00:00 GMTfinanceOwenhttps://pickuma.com/posts/index-funds-etfs-mutual-funds-what-differs/https://pickuma.com/posts/index-funds-etfs-mutual-funds-what-differs/The three labels overlap more than the marketing suggests. A developer-friendly breakdown of structure, tax treatment, and the cases where the difference actually changes your decision.Tue, 19 May 2026 00:00:00 GMTfinanceOwenhttps://pickuma.com/posts/polygon-vs-alpha-vantage-stock-data-apis-2026/https://pickuma.com/posts/polygon-vs-alpha-vantage-stock-data-apis-2026/Polygon and Alpha Vantage are the two common entry points for developer-side stock data. A side-by-side on free tiers, coverage, and developer experience — without the trading-edge hype.Tue, 19 May 2026 00:00:00 GMTfinanceOwenhttps://pickuma.com/posts/sec-edgar-fundamentals-api-for-developers/https://pickuma.com/posts/sec-edgar-fundamentals-api-for-developers/Most stock-data tutorials skip past the one free, public, no-rate-limit source for US company filings. Here's how to read fundamentals straight from SEC EDGAR, JSON-first.Tue, 19 May 2026 00:00:00 GMTfinanceOwenhttps://pickuma.com/posts/what-diversification-actually-buys-you/https://pickuma.com/posts/what-diversification-actually-buys-you/Diversification reduces idiosyncratic risk, not market risk. When the distinction matters, what correlation looks like under stress, and why 60/40 isn't a free lunch.Tue, 19 May 2026 00:00:00 GMTfinanceOwenhttps://pickuma.com/posts/what-rules-based-investing-actually-means/https://pickuma.com/posts/what-rules-based-investing-actually-means/Rules-based investing isn't AI, isn't HFT, and isn't a guarantee. It's a behavioral discipline: decide the action before the event. Here's what counts as a rule, what doesn't, and how it actually fails.Tue, 19 May 2026 00:00:00 GMTfinanceOwenhttps://pickuma.com/posts/why-finance-on-pickuma/https://pickuma.com/posts/why-finance-on-pickuma/Tools, evidence, and disclosure are the same job whether the topic is a code editor or a brokerage account. Here's the editorial line for the new finance section.Tue, 19 May 2026 00:00:00 GMTfinanceOwen