Title: Contingent valuation and public health: eliciting values from patients and the public
1Contingent valuation and public health eliciting
values frompatients and the public
- PAPER PRESENTED
- TO IDEP- GREQAM WORKSHOP
- By Cam Donaldson
- 23RD-24TH JUNE 2003
2- Political economy has to take as the measure of
utility of an object the maximum sacrifice which
each consumer would be willing to make in order
to acquire the object....the only real utility is
that which people are willing to pay for. - Jules Dupuit (1844)
3What I am not doing today
- Discrete choice/conjoint analysis
- Willingness to accept
- Conventional validity studies
- e.g. payment vehicles
- Mostly about enhancing the validity of WTP
studies with respect to relevance to
decision-makers.
4Outline
- Why WTP in health?
- Using the values in decision making
- Uptake of WTP studies
- Patients and the public
- Distributional issues
- Progress in eliciting values from patients
- Progress in eliciting values from the community?
5What are we valuing?
Productivity
Resource inputs
UTILITY
Healthy time
How resources are used, e.g. process, location
6WTP why we need it
- strength of preference
- can compare different goods
- pulls together several factors
- beyond health
- more in line with theory? Less restrictive on
- Mode of sacrifice
- Evaluation space
- Separability
7Uptake of WTP
- Do hypothetical questions give hypothetical
answers? - Comparisons to revealed preference
- Scope
- Still developing (CV/SG)
- Unethical to use in decision making?
- Perceptions and guidelines
- General problem with economics?
8Whose values?
- Whose values?
- Patients Public
- Private (1) (2)
- Nature of
- good Collectively (3) (4)
- financed
9USING WTP DATAfour main scenarios
- (1) Patients private good
- If WTP gt cost, implement
- (2) Public private good
- If WTP gt cost, implement
- (3) Patients collective good
- Three possibilities
- (4) Public collective good
- Need WTP and cost data for alternative uses of
resources
10WTP AND DISTRIBUTION OF INCOMECURRENT THINKING
- ..the validity of this approach rests upon some
important Paretian assumptions one being that
individuals are the best judges of their own
welfare, another being that the current
distribution of income is appropriate. - OBrien B and Drummond MF (1994) Statistical
versus quantitative significance in the
socioeconomic evaluation of medicines.
PharmacoEconomics, 5 389-398. - Cost-benefit analysiss primary valuation method
is willingness to pay(authors emphasis) (WTP),
an approach whose difficulty lies in its
intrinsic favouring of the programs and diseases
of the affluent over those of the poor - Gold M et al. (1996) Effectiveness in Health and
Medicine. New York, Oxford Univ Press, pXXII
11Distribution what to do?
- Universal problem QALYs have it too
- Leave values unweighted? (Pauly)
- Decision-making view (Currie et al., Little etc)
- Sensitivity tests (Boardman et al., Donaldson)
- Direction of preference
- Strength of preference within income groups
- Sensitivity of end results to different weights
12WTP for own care
- ask patients to value their own treatment
- example pre-natal CF testing
- both parents have to test positive
- disclosure versus non-disclosure
- 127 out of 176 in trial responded to WTP
questionnaire
13RESULTS FROM CF SCREENING STUDY
- (1) About 21!
- (2) No difference between groups.
- This result has been shown in other studies.
14CF follow up WTP for each
- make respondents aware of alternatives
- reference point theory
- example CF follow up
- non-trial sample of 450 pregnant women asked
about WTP for each method
15RESULTS FROM CF FOLLOW UP
- (1) Lower response rate.
- (2) 61 preferred disclosure 27 preferred
non- disclosure. - (3) Problems with validity.
16MATCHING OF PREFERENCES AND WTP
- Is WTPD gt or lt WTPND?
- Pref Less Equal Greater Total
- Disc 61 (17) 99 (28) 62 (17) 222 (62)
- Non-disc 78 (22) 16 (4) 94 (26)
- None 21 (6) 22 (6) 1 44 (12)
- N.B. 90 people did not respond to this question.
17MARGINAL APPROACH
- Give the respondent details of each alternative
(i.e. existing and alternative care) and ask
them - - which they prefer
- - what is the maximum amount they would be
willing to pay to have their preferred rather
than their less-preferred option. - This has been done in studies of
- - management of miscarriage
- - intra-partum care (postal open-ended)
- - parents views of services for children
(interview bidding).
18STUDY OF CHILD HEALTH SERVICES
- (1) 82 parents interviewed (out of 300 asked to
participate) - (2) Each parent was asked one WTP question
about each of three pairwise choices - inpatient stay versus day case for tonsillectomy
- hospital-based versus local clinics for
bedwetting - school health service to focus on all children or
those with special needs.
19RESULTS FROM STUDY OF CHILD HEALTH SERVICES
20WTP AND DISTRIBUTION
- Data on preferences allow us to analyse whether
richer people tend to prefer one option and,
therefore, whether mean (or median) WTP for that
option is a result of greater purchasing power
(i.e. ability to pay) as well as willingness to
pay. - Therefore, analyse preferences by
- - income
- - social class
21Distribution of preferences and mean WTP for
surgery by income group
- Income (s per week)
- lt100 100-150 150-230
230-350 gt350 - Inpatient 4 2 8 5 5
- 25 75 44 56
25 - Day case 5 2 8
4 6 - 32 50 86 77
43
22USING THE RESULTS
- (1)Assuming options are mutually exclusive, other
things (including cost) being equal, the option
to be implemented would be that preferred by
whichever group could compensate the other and
still remain better off. - (2)Where other things (e.g. cost) are not equal,
if the option with greater WTP (and hence
utility) also has a greater cost, the decision
maker then has to decide whether this extra cost
is worth incurring.
23BROADER PRIORITY SETTING
- 150 in Northern Norway were asked their maximum
WTP for three public sector health care
programmes - - a helicopter ambulance
- - 80 more elective heart operations per annum
- - 250 more hip replacements per annum.
- WTP RESULTS (NOK n143)
- Helicopter Hearts Hips
- 316 306 232
24Why WTP is important
- The highest valued QALYs are for the helicopter,
which might reflect a preference for the rule of
rescue. - Life saving is more highly valued than the same
QALY gain from life extension and life
improvement - If the results are valid!
25Problems with this method
- Rank orderings do not match WTP orderings
- Size of the good problems.
- Hence, EuroWill, to examine
- Can different countries do it?
- Various methodological issues (size of good,
closed-ended vs payment scale, informational
effects, marginal approach, econometric issues)
26Mean WTP (PPPGDP, 1999) using standard approach
27WHERE NOW FOR WTP?Conduct of studies
- Do not use WTP for own care
- Open-ended questions are problematic
- Use some form of payment vehicle
- Postal questionnaires require careful design
- Tests for effects of income/class are feasible
- Marginal approach has potential for choices
between close substitutes
28WHERE NOW FOR WTP?Recommendations for research
- Compare payment vehicles
- More testing of the marginal approach
- Extend to broader priority setting contexts
- EUROWILL
- External validity/strategic bias
29Positive outlook
- THE ECONOMIST OF OLD
- Knows the price of everything and the value of
nothing. - THE MODERN ECONOMIST
- Knows the price, and is some way towards knowing
the value, of health care at the margin.
30Or....
- ...MAUREEN LIPMANS MOTTO
- Lifes like a questionnaire. You didnt ask to
be sent it, cant think what the answers are, but
might as well fill it in and hope it gets a
laugh.