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Lower cumulative loss quantile

The lower quantile is q(c)=inf{l:F(l)≥c}, where F(l)=P(L≤l).

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Define the loss random variable

L is loss over one common horizon, with positive numbers representing loss and negative numbers gain. The cumulative distribution F(l) counts probability at or below l. Confidence c is a decimal probability strictly between zero and one in the mathematical definition.

Use the first cumulative crossing

q(c)=inf⁡{ℓ:FL(ℓ)≥c},FL(ℓ)=Pr⁡(L≤ℓ)q(c)=\inf\{\ell:F_L(\ell)\geq c\},\qquad F_L(\ell)=\Pr(L\leq\ell)

This is a declared lower loss quantile, not a sample-interpolation rule.

Keep equality at the boundary

In the original finite model, F(0)=0.70 and F(10)=0.95. The lower quantile at c=0.95 is 10 because equality satisfies the rule. A level strictly above 0.95 reaches the next loss, 50.

Read the equal-weight special case

For n equally weighted observed loss records sorted ascending, rank ceil(nc) implements this rule, counting from one. Interpolated sample percentiles are a different convention. The tool supports confidence 50%–99.99% and does not infer observation weights or exposure repricing.

Further references