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Insights for systematic investors
Long-form research on disciplined investing, AI-assisted analysis, and the operational side of running a retail portfolio.
Methodology
Rebalancing bands: the 5/25 rule and the quiet zone
Rebalancing is usually sold as a way to make money; its durable case is risk control — keeping a portfolio recognisable as the one that was chosen. How Swedroe’s 5/25 bands are computed at each target weight, why the trigger flips at a 20% target, why sixteen months out of eighteen the answer is "nothing has happened", and what a German taxable account does to the arithmetic of acting.
Read the essay →Methodology
Position sizing: the arithmetic behind the weights
The portfolio effect of any move is the position’s weight multiplied by that move — so a 30% decline costs 1.5% of the portfolio at a 5% weight and 6% at a 20% weight. Read backwards, that is a ceiling on damage. Plus why a position that triples from 10% arrives at 25% without anyone adding to it, and what each of the three sizing approaches keeps fixed.
Read the essay →Taxes
German portfolio transfer: the 30% fallback trap
Moving a German securities account is free and tax-neutral — until the acquisition data fails to travel with it. § 43a (2) sentence 7 EStG then computes withholding on 30% of the disposal proceeds rather than the gain, and it applies even where the sale produced a loss. What triggers it, a worked example at identical proceeds and three different cost bases, and how the annual tax return undoes it.
Read the essay →Taxes
Vorabpauschale 2027: base rate, dates, worked scenarios
One input is still missing — the 2027 Basiszins, which the Bundesbank derives from the yield curve on the first trading day of January and the finance ministry announces mid-month. Everything else is already fixed: the § 18 InvStG formula, the cap at the year’s actual gain, and the debit in early 2028. With scenarios per €10,000 at 2.5%, 3.0% and 3.5%, computed by the same function as our calculator.
Read the essay →Taxes
German capital-loss offsetting: two pots, one deadline
German banks net gains and losses only within themselves, so a loss at one broker never reaches a gain at another without a loss certificate — and § 43a (3) sentence 5 EStG gives you until 15 December, irrevocably. The share pot, the general pot, the order the allowance is applied in, a worked two-broker example, and why the derivatives pot and its €20,000 cap disappeared from withholding in 2026.
Read the essay →Tools
FX impact calculator: asset return vs. currency effect
Decompose the EUR return of a foreign-currency investment interactively: with rates quoted as foreign currency per 1 euro (ECB convention), total EUR return = (1 + asset return) × (1 + FX effect) − 1. Asset contribution, currency contribution and the cross term stated separately — worked through with fixed illustrative rates, labeled as examples, no live data.
Read the essay →Tools
Vorabpauschale calculator 2026: base rate 3.20%
Calculate the 2026 Vorabpauschale interactively: base rate 3.20% (BMF letter of 13 Jan 2026), the § 18 InvStG formula with cap and twelfths rule, partial exemption by fund type, church tax and the saver’s allowance — every figure derived from the shown formula, due date 4 January 2027.
Read the essay →Education
Sparer-Pauschbetrag explained: Germany's saver's allowance
Up to €1,000 of capital income per person per year stays tax-free (€2,000 joint) under § 20 (9) EStG. How the Freistellungsauftrag distributes the allowance across banks, the order of loss offsetting, the interaction with the Vorabpauschale, and one worked year — every figure computed from the stated inputs.
Read the essay →Education
TER explained: what the total expense ratio covers — and what it does not
The TER bundles a fund’s ongoing charges but leaves out internal transaction costs, spreads, swap fees and every investor-side cost. What the figure means, a 30-year cost-drag table computed from its formula at render time, and why tracking difference is the fuller real-cost lens.
Read the essay →Education
Sharpe ratio explained: what the metric tells you — and what it does not
Excess return divided by volatility: (Rp − Rf) / σ. What the Sharpe ratio can compare (same period, frequency and risk-free basis), what it cannot (different windows, asymmetric return profiles), and its known limits — with example values computed from the formula at render time.
Read the essay →Tools
Simply Wall St alternatives in 2026: an honest comparison
What Simply Wall St does well, where people look elsewhere, and five alternatives read against the same six criteria — data coverage, methodology transparency, portfolio tools, AI labelling, pricing model, and jurisdiction. A factual matrix (Acutic included and disclosed), dated July 2026, with no podium and no ranking.
Read the essay →Methodology
Ten behavioral mistakes — and the system fix for each
Biases are workload failures, not character flaws — which is why willpower rarely fixes them but systems do. Ten well-documented investing mistakes, from loss aversion and the disposition effect to home bias and sunk cost, each paired with a one-line mechanism that blunts it: position caps, decision journals, blackout windows, checklists, review cadence.
Read the essay →Portfolio analysis
In GermanTWROR vs. IRR: why your tracker shows a different return
Two trackers, two returns for the same portfolio — both correct. Here's why: the time-weighted rate of return (TWROR) measures the strategy and strips out deposits, while the internal rate of return (IRR) measures your timing. The same worked example run both ways shows why the numbers diverge — and which metric is good for what.
Read the essay →Methodology
How often should you check your portfolio? What the data says
The checking paradox: the more often you look, the more red you see, and the worse you tend to decide. The probability of a negative return at daily, weekly, monthly and annual horizons — computed from stated assumptions — the research behind myopic loss aversion (Benartzi & Thaler, 1995), and a two-tier protocol that separates automated rule-watching from human review.
Read the essay →Taxes
In GermanAccumulating vs. distributing: the tax difference in numbers
Where exactly the tax difference between accumulating and distributing ETFs comes from — and how small it often is. A worked 10-year example (€10,000, identical gross return), the role of the Vorabpauschale (advance lump-sum tax) and the Sparerpauschbetrag (saver's allowance), and why the difference is mostly deferred tax, not saved tax.
Read the essay →Methodology
How to benchmark your portfolio (beating the S&P 500 is the wrong question)
Why “did I beat the S&P 500?” is the wrong question for a multi-asset portfolio: how to build a blended benchmark that matches your allocation, why deposits distort a naive return comparison, risk-adjustment in plain terms, and a four-step protocol — every performance gap expressed in percentage points.
Read the essay →Methodology
Portfolio concentration: how much in one stock is too much?
The single-name bands practitioners commonly cite and why they vary, what diversification actually removes, the hidden overlap when your funds all contain the same mega-caps, and how to measure your own concentration with the Herfindahl index — worked through with a threshold ladder and effective-holdings math.
Read the essay →Taxes
In GermanTeilfreistellung for ETFs: the 30% explained simply
Why part of your fund income stays tax-free: the Teilfreistellung (partial exemption) rates under § 20 InvStG (30% equity funds, 15% mixed funds, 60/80% real-estate funds), the equity ratio required and where to look it up, plus a worked example — €1,000 distribution, €79.12 difference.
Read the essay →Taxes
In GermanVorabpauschale explained simply (with worked examples)
The annual advance taxation of accumulating funds, step by step: the formula (fund value × base rate × 0.7), the base-rate (Basiszins) series up to 3.20% for 2026 per the BMF, a worked example per €10,000, and the interplay with the Teilfreistellung — every figure derived from the formula.
Read the essay →Education
ROIC vs ROE vs ROCE: what each measures, with one worked example
Three return-on-capital ratios that look interchangeable and are not. Each formula unpacked — what the numerator and denominator include and exclude — the ways each one flatters or misleads, and all three computed for Microsoft’s FY2025 10-K with every input cited from SEC EDGAR.
Read the essay →Tools
Parqet, getquin & co. compared
Tracking, analysis, and community are three different products under one category name. Import routes, return types, tax view, pricing, and connection model — a feature matrix built from the providers' primary sources, dated July 2026, with no ranking.
Read the essay →Education
The investment decision journal (free template + why it works)
A dated thesis written before the money moves is the only version of your reasoning hindsight cannot edit. The behavioral evidence from Fischhoff to Klein, a seven-field template you can copy, and the review ritual that turns entries into process.
Read the essay →Guides
comdirect: exporting your Depot and transactions as CSV
comdirect publishes no format specification at all — so this one is reverse-engineered. The documented Umsätze (transactions) route and its 540-day wall, the quieter Depot export, the two files' opposite encodings (ISO-8859-1 vs UTF-8 with BOM), and the holdings export nobody can confirm.
Read the essay →Privacy
Portfolio trackers without a bank connection: what your data is worth
PSD2 covers payment accounts — not securities accounts, which is why depot connections rest on commercial arrangements rather than a regulated right. What the aggregators are, what four trackers' own privacy policies say verbatim, and what the CSV model costs in convenience. With an eight-point GDPR criteria list.
Read the essay →Guides
DKB Depot export: what actually works in 2026
The DKB Depot has no CSV export for securities — the route that works is the Wertpapierabrechnung PDFs from the Postfach. The step-by-step path, a field-by-field table of what a confirmation carries and what an import reads, retention windows, and the pitfalls.
Read the essay →Guides
flatex Depot export: what actually works in 2026
flatex has no comprehensive CSV export — the route that works is the Wertpapierabrechnung PDFs from the Dokumentenarchiv (Postbox). The step-by-step path, a field-by-field table of what a confirmation carries and what an import reads, the 100-document display limit, and the pitfalls.
Read the essay →Guides
ING Depot export: what actually works in 2026
The ING Direkt-Depot has no CSV export — the route that works is the Wertpapierabrechnung PDFs from the Post-Box. The step-by-step path, a field-by-field table of what a confirmation carries and what an import reads, retention windows, and the pitfalls.
Read the essay →Guides
Scalable Capital: exporting your Depot as CSV
Scalable Capital exports transactions natively as CSV — but the button lives on the web, launched as a paid-tier feature, and the December 2025 Baader Bank migration split the history in two. Steps, every column explained, edge cases.
Read the essay →Guides
Exporting your portfolio from Interactive Brokers (Flex Queries)
IBKR has three export doors — Activity Statement, Flex Query, Flex Web Service — and one clearly better default for portfolio tracking. A Flex Query configured step by step, CSV vs XML, date-range limits, and the quirks that break imports.
Read the essay →Education
The stock research checklist (with a worked example)
Twelve checks in four blocks — business, financials, valuation context, risk — each one a question with a named free source. Run end to end on Apple’s FY2025 10-K, every figure cited, with a scorecard of what a finished pass looks like.
Read the essay →Education
How to read a 10-K in 30 minutes
A 10-K is organised by regulation, not by usefulness. The timed reading path through Items 1, 1A, 7 and 8, the red-flag patterns worth a second look, and a worked 30-minute pass on Apple’s FY2025 filing — every figure cited from EDGAR.
Read the essay →Guides
Your portfolio vs. the MSCI World: the fair comparison
An index has no savings plan — which is why contributions distort every naive return comparison. Time-weighted returns (TWROR), the shadow-portfolio method with identical cashflows, and the four most common comparison mistakes, with a worked example.
Read the essay →Education
10-K vs 10-Q: what each filing tells you (and which to read first)
One audited annual filing, three unaudited quarterlies — and very different reading value per section. Cadence, deadlines, what only the 10-K contains, what the 10-Q is actually for, and a practical which-to-read-when table with EDGAR links.
Read the essay →Portfolio analysis
In GermanConcentration risk in your portfolio: spot it, measure it, limit it
Concentration risk in a portfolio, taken apart: the four levels it appears on, what a −30% move in a 25% position costs in plain arithmetic, the Herfindahl index made intuitive, and the MSCI World's own 72% US weight — every figure cited.
Read the essay →Methodology
What is a stock quality score — and how is one built?
Quality is the most measurable factor family in investing. What goes into a quality score — ROIC, margin stability, accruals, leverage — the research behind each ingredient, and a worked example on Microsoft’s FY2025 10-K, every figure cited.
Read the essay →Methodology
Can you trust AI stock analysis? A checklist for opening the black box
Trust in an analytical tool is not a feeling — it is a property you can check. The documented failure modes behind the scepticism, what “trust” should mean for software, and a seven-question verifiability checklist you can put to any tool in the category.
Read the essay →Guides
Trade Republic CSV export: the 2026 guide
Trade Republic shipped a native CSV transaction export in April 2026 — most guides still say it does not exist. The exact menu path, what each field means, the known quirks, and the PDF fallback.
Read the essay →Methodology
A field guide to AI stock scores
Five AI stock-scoring systems — Danelfin, Kavout Kai, Seeking Alpha Quant, Simply Wall St Snowflake, TipRanks Smart Score — read methodologically. What each one actually measures, where each one fails honest scrutiny, and a seven-question checklist for what to ask before paying.
Read the essay →Tools
The self-directed investor’s 2026 stack
Seven tools, seven jobs. An honest tool-by-tool reading of Koyfin, Sharesight, Simply Wall St, Getquin, Parqet, Stock Rover, and Alpha Spread — and the workflow gap the European stack still leaves open.
Read the essay →Methodology
Five things to check before trusting an AI research summary
AI can write a confident research summary in seconds. Confidence is not accuracy. A five-point checklist for deciding whether an AI-generated investment summary has earned your trust.
Read the essay →Education
The difference between investment research and investment advice
Research and advice are two different products with two different legal definitions. A plain-English account of how they differ, why it matters for a self-directed investor, and why doing your own research is doing the work properly.
Read the essay →Regulation
What changes for AI investing tools on 2 August 2026
Three EU AI Act provisions take effect this summer. A plain reading of what each one requires of AI investing tools, and a buyer's checklist for what to look for if your tool is silent on any of them.
Read the essay →Methodology
How to build a portfolio with rules you actually keep
A first-principles essay on investment rules for the retail investor — why most people break their own rules quietly, what that costs, and what an enforcement system has to look like.
Read the essay →