Definition:Increased limits factor (ILF)
📊 Increased limits factor (ILF) is a multiplicative rating factor used in commercial liability insurance to adjust the base-rate premium — which corresponds to a standard, or "basic," policy limit — upward when a policyholder purchases higher limits of liability. In practice, if the basic limit for a commercial general liability policy is $100,000 per occurrence, the ILF tells the underwriter how much additional premium to charge when the insured opts for $500,000 or $1 million instead. The factor is expressed as a ratio relative to 1.00 at the basic limit, so an ILF of 2.50 means the premium at the selected limit is two and a half times the basic-limit premium.
⚙️ ILFs are derived from actuarial analyses of loss distributions — specifically, how the severity tail of claims behaves at progressively higher dollar thresholds. Because large claims are relatively rare, each incremental increase in the policy limit adds proportionally less expected loss, which is why ILFs rise at a decreasing rate. Rating organizations such as the Insurance Services Office (ISO) publish standard ILF tables for major liability lines, segmented by coverage type and sometimes by hazard group. Carriers may adopt these tables as filed, modify them to reflect their own loss experience, or develop proprietary factors — especially for specialty or excess and surplus lines risks where standard tables may not capture the true tail behavior.
💡 Selecting the right ILF table — or knowing when to deviate from one — is a significant source of competitive differentiation among carriers and MGAs. An insurer that underestimates severity in the tail will charge too little for high limits and attract adverse selection from sophisticated buyers, while an insurer that overcharges will lose business to competitors with sharper pricing. Insurtech analytics teams increasingly use predictive modeling and large-loss simulation to refine ILF curves beyond what traditional aggregate data supports, particularly in lines like cyber liability and D&O where loss development patterns are still maturing.
Related concepts: