Why Liability Limits Are The Wrong Place To Economise

Every policy has a coverage that is cheap in absolute terms and enormous in consequence. On an auto policy that coverage is liability, and it is routinely the first thing a driver cuts when the renewal arrives higher than expected.

That instinct is understandable and almost always wrong. The reason is a structural feature of how liability is priced, and once you see it, the decision becomes straightforward.

What the three numbers mean

Liability limits are usually written as three figures — something like 100/300/100. They are not a code. They are, in order, the per-person bodily injury limit, the per-accident bodily injury limit, and the property damage limit, all in thousands of dollars.

So 100/300/100 means: up to $100,000 for injuries to any one person, up to $300,000 for all injuries in a single accident combined, and up to $100,000 for damage you cause to other people's property. Some policies instead offer a single combined limit, one figure covering both injury and property damage in aggregate.

Required minimums are set by each state and differ substantially. Several states' minimums were written decades ago and have not tracked medical or vehicle repair costs. A property damage minimum that felt generous when a new saloon cost a fraction of today's price does not go far against a modern vehicle with sensor-laden bumpers and a calibration bill attached to every panel. The gap between "legally compliant" and "adequately covered" is, in many states, very wide.

Note also that a handful of states run no-fault or add-on personal injury protection regimes that change how first-party medical costs are handled. That affects the shape of the policy but not the underlying point about third-party liability limits.

The pricing asymmetry, with a worked example

Here is the mechanism. Most liability claims are small. The large ones are rare. Because the higher layers of a liability limit are only ever touched by the rare severe claim, the expected cost of providing those layers is low — and the price reflects it.

Assume a driver is quoted the following on the same policy, same everything else. These are illustrative figures for the purpose of showing the shape; your own quote will differ by state, carrier and driver, and you should run this on your actual numbers.

Suppose state-minimum limits cost $520 a year, and 100/300/100 costs $680. The step up costs $160 a year. What did $160 buy? If the state minimum were 25/50/25, it bought an additional $75,000 of per-person bodily injury protection, an additional $250,000 per accident, and an additional $75,000 of property damage.

Now do the second step. Suppose 250/500/100 costs $760 — another $80 a year for another $150,000 per person. The second $80 bought roughly twice the incremental protection that a portion of the first $160 did. That is the asymmetry: as you climb, each dollar of premium buys more coverage, not less.

This is the opposite of how most goods work, and it is why the honest advice is to price the step up before dismissing it. Drivers who assume higher limits are proportionally more expensive often discover the difference is a fraction of what they feared.

What the limit is actually protecting

The vehicle is not the point. Collision coverage handles your car. Liability handles what happens to everyone else, and — critically — what happens to you if the damages exceed your limit.

When a judgment or settlement runs past the policy limit, the balance does not evaporate. It attaches to the person, and depending on state law it can reach savings, investments, home equity and, through wage garnishment, future earnings. The exemptions vary considerably by state, so no universal statement is possible about what is protected. What is universal is that the exposure is personal and it is open-ended in a way the policy limit is not.

This is why the calculation is not "what can I afford to insure" but "what could be taken from me." A driver with meaningful assets and minimum limits has a mismatch, and it is not a mismatch that reveals itself gradually.

Anyone carrying substantial assets should also ask about an umbrella policy, which sits above the auto and homeowners limits. Umbrella cover generally requires specified underlying limits before it can be written at all — another reason the auto liability limit is a foundation rather than a line item.

Where to economise instead

The economising instinct is not wrong; it is misdirected. The place to take risk deliberately is the deductible, because that exposure is bounded, known in advance, and something you can decide to absorb. There is a method for setting it in choosing a deductible you can actually absorb.

The other lever is not to shrink the coverage but to re-price it. Carriers weight rating factors differently and file those plans with state regulators, which is why the same driver with the same declarations page can receive materially different quotes. The mechanics are covered in how carriers price you.

Trim the deductible. Shop the carrier. Leave the liability limit alone.