A good backtest starts the questions, it does not end them
How to distinguish an attractive backtest from a result that is reproducible, robust and investable after costs.
August 2026
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The people who manage client money at JonatanMars Invest write these articles. We cover markets, fees and tax, and we say what we don't know. You won't find tips on which stock to buy.
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Featured · August 2026
How many stocks make a diversified portfolio?
A stock count alone does not tell you how diversified a portfolio is. Weights, shared exposures and behaviour during bad periods matter too.
Latest
August 2026
A smooth chart does not make an investment safe
Volatility is useful, but it does not capture permanent loss, liquidity, inflation or rare events. A smooth chart is not proof of safety.
August 2026
Value, momentum and quality: three factors in plain language
What value, momentum and quality measure, why they may persist, and why each can disappoint for years.
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