No topic in California workers’ compensation produces more confusion than this one, and the confusion is not the injured worker’s fault. The system uses two different percentages that sound like the same thing and are not.
Someone asks whether 20 percent whole person impairment means they are 20 percent disabled. Someone wants to convert a 17 percent rating into permanent disability. Someone received a report showing 0 percent impairment for one body part alongside a much higher permanent disability figure and cannot make sense of it. Someone else wants to know whether 15 percent PD and 15 percent WPI are the same, and what apportionment does to either.
So let me put the answer in a heading, because it is the single most useful thing on this page.
Whole Person Impairment Is Not Permanent Disability
Whole person impairment is a medical measurement. A physician evaluates you under the AMA Guides and assigns a WPI percentage describing how much your body is impaired. That is a doctor’s finding.
Permanent disability is a legal rating. It starts with WPI and then runs through a series of adjustments before it becomes the percentage that determines your benefits.
They are different numbers, produced by different people, for different purposes. Permanent disability is almost always the higher number, which is why workers who read only the WPI figure in their report often think their case is worth far less than it is.
What California Workers Are Asking on Reddit About Ratings
- I got 20 percent WPI. Does that mean I am 20 percent disabled?
- How do I convert WPI into permanent disability?
- My report shows 0 percent for one thing and 30 percent overall. How?
- Is 15 percent PD the same as 15 percent WPI?
- What is apportionment and why did it cut my rating?
- How much money is a percentage point actually worth?
How WPI Becomes PD
- The evaluator assigns whole person impairment under the AMA Guides for each affected body part.
- An adjustment factor is applied. For injuries on or after January 1, 2013, WPI is multiplied by a uniform 1.4 factor. For older injuries a diminished future earning capacity rank was used instead, which is why rating rules differ by date of injury.
- An occupational adjustment is applied. Your job is assigned an occupational group, and the same impairment produces more disability in a physically demanding occupation than in a sedentary one. A shoulder impairment matters more to a roofer than to an accountant, and the rating reflects that.
- An age adjustment is applied. Older workers generally receive an upward adjustment, on the reasoning that adaptation and retraining are harder.
- Multiple impairments are combined, using a combining method rather than simple addition, so two 20 percent impairments do not produce 40 percent.
- Apportionment is subtracted.
This is why a 20 percent WPI is frequently not a 20 percent disability. Run through the adjustments, it commonly lands meaningfully higher. And it is why two workers with identical impairment can end up with different ratings based only on their age and their job.
Why a Report Can Show Very Different Numbers
Reports frequently contain several percentages that mean different things: WPI for one body part, WPI for another, a combined figure, and then a final rating string. A 0 percent impairment finding for one body part is entirely compatible with a substantial overall rating driven by a different body part. If your report shows numbers that do not seem to reconcile, that is usually what is happening, and it is worth having someone read the rating string with you.
Apportionment, and Why It Cuts Your Rating
This is where most of the money is won and lost, and it is the part that feels least fair to injured workers.
Under Labor Code section 4663, permanent disability is apportioned between causes. The evaluator must address what percentage of your disability was caused by the industrial injury and what percentage by other factors, including pre-existing conditions and degenerative changes.
So a 30 percent disability with 40 percent apportioned to non-industrial causes yields substantially less than a 30 percent disability with no apportionment. The rating is the same. The money is not.
Apportionment must be based on substantial medical evidence, not speculation. An evaluator cannot simply gesture at your age or at degenerative findings on an MRI and assign a percentage. Apportionment opinions that lack a reasoned explanation are challengeable, and challenging them is one of the more valuable things an attorney does in a case like this.
What the Percentage Is Worth
Permanent disability is paid as a number of weeks of benefits, and the number of weeks per percentage point increases as the rating rises. This is important and widely misunderstood: the relationship is not linear. Going from 10 percent to 20 percent adds far less value than going from 60 percent to 70 percent, because the higher bands pay more weeks per point.
A rating of 100 percent is permanent total disability and is paid for life.
The weekly permanent disability rate is capped, and the cap is low relative to most people’s wages, which is why permanent disability awards often feel small compared to what the injury actually cost someone. That reaction is understandable. The rate is set by statute rather than by what seems fair.
Common Misconceptions
That WPI and PD are the same number. They are not. WPI is a medical measurement, PD is a legal rating derived from it.
That the percentage describes how disabled you feel. It does not. It is a formula output, not a description of your life.
That two people with the same rating get the same money. Apportionment, date of injury, and the weeks-per-point structure all change the result.
That impairments add together. They are combined using a method that produces less than simple addition.
That apportionment is automatic. It must rest on substantial medical evidence, and unsupported apportionment can be challenged.
That doubling the rating doubles the money. Higher ratings pay more weeks per point, so value rises faster than the percentage does.
If You Just Received a Rating
- Identify which numbers are WPI and which is the final PD rating. They are not interchangeable.
- Check that every injured body part was addressed. Omitted body parts are a common and costly error.
- Read the apportionment discussion closely. Is there an actual medical explanation, or a bare conclusion?
- Confirm your occupational group is correct. A wrong occupation code changes the rating.
- Confirm your date of injury, which determines which rating rules apply.
- Do not accept a rating as final without having it reviewed. Rating errors are common and correctable while the case is open.
Frequently Asked Questions
Does 20 percent WPI mean I am 20 percent permanently disabled?
No. Whole person impairment is a medical measurement under the AMA Guides. Permanent disability is a legal rating derived from it after adjustments for the statutory factor, your occupation, and your age, then reduced by any apportionment. The final permanent disability rating is usually higher than the WPI figure.
How do you convert WPI to permanent disability in California?
For injuries on or after January 1, 2013, whole person impairment is multiplied by a uniform 1.4 factor, then adjusted for occupational group and age, combined with any other impairments, and reduced by apportionment. Injuries before 2013 used a diminished future earning capacity rank instead of the 1.4 factor.
Is PD the same as WPI?
No. WPI is the physician’s impairment measurement. PD is the legal disability rating that determines your benefits.
What is apportionment in California workers’ comp?
Under Labor Code section 4663, permanent disability is divided between industrial and non-industrial causes. Only the industrial portion is compensable. Apportionment must be supported by substantial medical evidence rather than assumption.
Why is my permanent disability rating lower than my impairment suggests?
Most often apportionment, an incorrect occupational group, or body parts omitted from the rating. Each is worth checking, and each is correctable while the case remains open.
Does a higher rating mean proportionally more money?
No. Permanent disability pays a number of weeks that increases per percentage point as the rating rises, so higher ratings are worth disproportionately more. A rating of 100 percent is permanent total disability, payable for life.
Have Your Rating Checked Before You Settle
Rating errors are common, and once a case resolves they are very hard to fix. If you have a report with numbers you do not understand, or an apportionment opinion that seems unsupported, contact my office for a free consultation.
Ryan D. Kayrell, PC represents injured workers throughout California from Irvine, Orange County. This page is general information about California workers’ compensation law, not legal advice for your situation, and reading it does not create an attorney-client relationship. Rating rules vary by date of injury. Questions described here are paraphrased from public online discussions and do not reflect any client of this firm.