Should the idle cash sit in Treasury bills?
12 November 2026 · a study on MonsterDesk's own paper account and its own tests
- Question
- Half of the account follows one fixed rule: the S&P 500 and the Nasdaq-100, each held only while above its 200-day average, and cash otherwise. Cash in a paper account earns nothing. Would a Treasury-bill fund in place of that cash add to the result?
- What we did
- Ran the rule on real prices from 2008 both ways, charging the same 0.05% for every switch.
- What it showed
- Almost no difference.
Return a year. About a fifth of the money was in cash on an average day, bills paid close to nothing for most of those years, and with bills every switch trades two funds instead of one.
Period Cash Treasury bills 2008 to 2026 10.61% 10.54% Last ten years 13.96% 14.07% Last three years 17.56% 17.79% - What changed
- Nothing. A gain of 0.1 to 0.2 points a year does not justify another moving part in the account. We will look again if the rule spends a long spell in cash while bills pay well.
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