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Expert views on most suitable monetary incentives on food to stimulate healthy eating

Wilma E. Waterlander , Ingrid H. M. Steenhuis , Emely de Vet , Albertine J. Schuit , Jacob C. Seidell
DOI: http://dx.doi.org/10.1093/eurpub/ckp198 325-331 First published online: 15 December 2009

Abstract

Background: Pricing strategies are an important component in the marketing mix and may also be useful in stimulating healthier food choices. However, due to competing interests and feasibility problems, the introduction of pricing strategies is complicated. For successfully introducing food pricing strategies, it is essential to explore incentives that are not only promising but also realizable and being approved by different sectors. Methods: We aimed to assemble a list of pricing strategies by exploring expert views using the Delphi method. Subjects included experts from academia, industry, retail, agriculture, policymakers, consumers and non-governmental organizations. Data were collected in three rounds. In round one, experts designed promising pricing strategies. Based on a time-budget model incorporating Sleep, Leisure, Occupation, Transportation and Home-based activities, these strategies were in the subsequent rounds judged on several criteria. Results were analysed using median and interquartile deviations scores. Results: We found fair consensus levels among experts and a varied list of promising pricing strategies. The panel agreed on the potential success of offering small presents, providing price-cuts on healthy foods and discounting healthier foods more frequently. Also, it was found that experts gave higher rates to pricing strategies for which the implementation responsibilities could be placed elsewhere. Conclusion: The resulted list of promising monetary incentives is an essential first step for the future design of pricing strategies. Following this study, it is important to determine how to make solid agreements on responsibility and implementation issues. Also, consumer perceptions regarding the proposed pricing strategies should be studied.

  • Pricing strategies
  • food
  • interventions
  • prices
  • healthy eating

Introduction

In most countries, the majority of the population does not eat according to dietary guidelines, especially among lower socio-economical groups.1,2 One option to stimulate healthy eating is by the use of pricing strategies. Sales promotions form an important part of the marketing mix and are widely used to stimulate consumers to buy certain products.3

Different studies have shown that price is indeed an important determinant in food choice.4–6 Also, it is shown that diet quality and diet costs are positively correlated.7–9 Food choice in general, and the healthier food choice in particular, may therefore be subjective to economic factors.10 For that reason, pricing strategies seem a fitting intervention to stimulate healthy eating. Yet, the introduction of food price measures is complicated. Previously suggested monetary incentives such as taxes or subsidies11,12 that have proven to be effective in decreasing the prevalence of tobacco and alcohol use13,14 seem complex to implement. Unlike tobacco and alcohol, food is a basic element for survival and the discrimination of healthy versus unhealthy foods is not well established.12,15,16 Also, divergent involved sectors and feasibility issues may raise barriers to the deciding stages of the introduction of food price strategies.15

Nevertheless, both opinion-based and scientific articles have suggested that pricing strategies can be a useful tool in changing dietary behaviour.17–20 A wide exploration of potential pricing strategies, including and going beyond taxes and subsidies, might form a solution for the listed barriers. This exploration could include the potential use of strategies known from marketing literature such as ‘premium promotions’ or ‘sampling promotions’3 and could focus on strategies that are approved by different sectors involved.

A well-founded method that has found to be of great value in creating consensus among complex problems is the Delphi method.21–23 This article describes the results of such a Delphi study by aiming to assemble pricing strategies that may be feasible for implementation and are promising in stimulating healthier food choices.

Methods

Characteristics of the Delphi method

Key features of the Delphi include the use of experts, different rounds, controlled opinion feedback and giving participants the possibility to change their opinions.23,24 Our study was designed in line with those features. Comparable with other Delphi studies, we departed at some points from the original Delphi.25 The results were obtained in the Netherlands and included multinational viewpoints.26 Methods and procedures of this study were approved by the Medical Ethical Committee of VU University Medical Centre Amsterdam.

First round

Sample

In order to create a representative expert panel, we first identified the most important involved sectors, namely: (i) academic research, (ii) food processing, industry, retail, agriculture and (iii) policymakers, public interest and non-governmental and consumer organizations. Four researchers made a list of organizations and institutions from these sectors. From this list, key individuals were indicated, resulting in 81 experts. These experts were sent a postal invitation and were asked to take part in all three Delphi rounds. Table 1 shows the number of invited and participated experts for the different rounds and their expertise. The total panel size of the first round was 29 (response rate 36%). This panel may have been biased since experts may have decided to participate because they were interested in the topic. Still, we made effort to create a heterogeneous panel, which included experts with a high position in their organization. As Table 1 shows, the non-response was similar in all three sectors, and there were no signs of selective drop-out. All experts were native Dutch.

View this table:
Table 1

Participating experts in the Delphi study and response rates per round, per sector and per expertise

Graphic
  • *m = male; f = female

  • a: Two experts dropped out: one from a semi governmental research centre and one from a retail/branch organization

  • b: 61% of the participants in the second round were participant in the first round, 29% were additionally selected with a response rate of 43%.

  • c: 8 experts dropped out: one from a retail/branch organization; two from food consultancy; one expert from the Food Council 1 expert on economics; two experts on food and health; and one expert from a semi governmental research centre.

  • d: 82% of the participants from the second round also joined the third round

  • e: The third round consisted for 64% of original participants from the first round

Ideation session

Comparable with the classical Delphi, the first round was designed to discover ideas using open-ended questions.23 For this purpose, we organized an ideation session in which the experts had a structured discussion. The use of an ideation session departs from the original Delphi since no anonymity could be provided. However, this method provided the opportunity for an open debate in which experts from different sectors could familiarize with interests of importance in other fields. Also, active participation may enlarge further cooperation.22

The ideation session consisted of two general discussion and two brainstorm rounds enabling us to discuss the two major types of pricing strategies (stimulating ‘healthy’ eating and discouraging ‘unhealthy’ eating) separately. In the brainstorm rounds, experts discussed in smaller subgroups and were instructed about the focus of the session and assigned to discussing exclusively price incentives.

Data analyses

The ideation session resulted in a list containing multiple pricing strategies. These strategies were inductively categorized into subcategories, a method regularly used in qualitative data analysis.27 Subsequently, comparable subcategories were combined into larger categories and overlapping strategies were redefined as 1, resulting in four broad categories and 29 strategies that were questioned in the second round (Table 2).

View this table:
Table 2

Pricing strategies resulting from the 1st round and questioned in the 2nd round (scores based on a seven-point Likert scale)

Items resulting from the first Delphi round2nd round scores
Mdn EffectivenessIQD a
A. Taxes:
A1*Healthy food options at a lower VAT rate42
A2*Calorie charge: charge based on energy density and nutrient density43
A3Tax rise on unhealthy food items33
A4Introduction of a special tax on fabricated products22
A5Extra taxes on unhealthy raw produce (sugar/fat)32
B. Government interference and insurance system:
B1Extra food allowance for low income groups23
B2Insurance premium reduction when a healthy diet is followed32
B3Extra governmental allowance to retailers to make healthy food items generally less expensive42
B4*Bonus for low income consumers assigned when a certain amount of healthy products are purchased32
B5More expensive license for purchase settings when a certain amount of unhealthy products are sold23
B6Prohibit special offers on unhealthy food items34
C. Way of offering and presentation:
C1*Post with recipes: healthy, easy, and cheapb42
C2*Offering an additional healthy product for free on the purchase of a healthy product42
C3*Offering small presents/extras with healthy food itemsb42
C4*Two healthy products for the price of one42
C5*Savings stamps on healthy food items along with attractive actionsb42
C6Quit quantity rebate on unhealthy food items33
D. Price and Discount strategies:
D1*Healthy food options more often on special offerb52
D2*Sudden price rise for unhealthy food items3.53
D3*Combination discount: offering discounts on daily or weekly meal optionsb42
D4*Offering the healthy option of comparable products for a lower priceb42
D5Stickers to receive discount on self-selected healthy products32
D6Food coupons to receive discount on healthy food items exclusively for low income groups32
D7Direct discount on healthy food items with a discount card exclusively for low income groups33
D8*Price cuts on healthy food itemsb42
D9Making healthy products relatively cheaper by offering them in larger amounts for the same price32
D10Portion size: making unhealthy products more expensive by reducing portion sizes33
D11*Making unhealthy products more expensive in order to finance subsidies on healthy food items43
D12*Making both healthy food items cheaper and unhealthy food items more expensive43
  • *Selected for the third round, based on a median score of ≥3.5 on the item effectiveness (scale 1–7)

  • a: IQD = Inter Quartile Deviation; indicates the distance between the 25th and the 75th percentiles

  • b: Median score ≥3.5 on all eight criteria in the second round

Second round

Sample

Participants in the second round included experts from the first round and an additional group for broadening knowledge and viewpoints. Both experts recommended by first-round participants and experts who were not able to join the first round but indicated an interest in taking part in the subsequent rounds were invited. Of the first-round participants, n = 27 (93%) also completed the second round. For the additional group, n = 35 experts were invited, of which n = 17 agreed to participate and completed the questionnaire (49%). The total panel size in this round was 44 (Table 1).

Questionnaire

In the second round, experts were asked to evaluate the first-round strategies. They received a postal questionnaire and were requested to judge the strategies based on eight criteria using a 7-point Likert scale. The design of those criteria was started from the Sleep, Leisure, Occupation, Transportation and Home-based activities (SLOTH) model. SLOTH is an economic model used to indicate how people allocate their resources of money and time in order to maximize utility. The model contains four main factors that can be used to prioritize interventions: economic efficiency, equity, effectiveness and feasibility. Some factors contain sub-factors; feasibility contains for example: legality, politics and public popularity.28,29 SLOTH was used since it combines economic, political and public health perspectives and is a sufficient guide in determining promising economic measures, which fits well with our research aims.23,29 To refine the four factors from SLOTH, the sub-factors, a previously conducted Delphi study on tobacco policy, together with the literature on complicating factors surrounding food pricing strategies were used.30 Based on these three sources, eight criteria were designed which were judged suitable to give an all embracing judgement about the food pricing strategies:

  • (i) Political feasibility—Is the intervention achievable from a political viewpoint?

  • (ii) Practical workabilityIs the intervention practical doable?

  • (iii) Opportunities for implementationTo what extend can the intervention be carried through on the long run?

  • (iv) Effectiveness—Does the intervention have a sufficient effect size/impact?

  • (v) AffordabilityTo what extent is the intervention affordable in the long term?

  • (vi) Social justice—To what extent is the intervention justifiable for different socio-economical groups?

  • (vii) Consumer acceptanceTo what extent is the intervention acceptable from the viewpoint of consumers?

  • (viii) Industry acceptance—To what extent is the intervention acceptable from the viewpoint of the industry/producers/retail?

Data analyses

First, it was analysed whether the eight criteria used in the questionnaire were independent scales using Kendall’s tau non-parametric correlation matrix. Second, we analysed the extent to which each individual expert agreed with the strategies using median scores. The scores ranged from 1 to 7, and a cut-off point of 3.5 was used to indicate that experts agreed with the strategy. The conservative cut-off point of 3.5 was chosen since it was considered important that strategies were not excluded from further consideration too easily. Third, the level of consensus between experts was analysed using interquartile deviations (IQDs). IQD is a measure of statistical dispersion and indicates the distance between the 25th and the 75th percentiles. A smaller IQD represents a larger consensus, and an IQD ≤ 1 indicates a good consensus.23

Third round

Sample

Participants from the second round were also invited to the third round. Of the total sample, 64% completed all three rounds (Table 1).

Questionnaire

Preceding the third round, experts were provided with statistical group feedback from the second round. Based on this feedback, experts were given the opportunity to change their answers. In the third round, we further examined the strategies that had been indicated as potentially effective in the second round. Strategies were found to match this criterion if they had a median score ≥ 3.5 on effectiveness. Also, strategies were judged on low consensus scores (IQD ≥ 1). In total, 15 out of the original 29 strategies fulfilled these criteria and were again proposed to the experts using an electronic questionnaire. For a second time, experts were asked to judge the 15 strategies on the eight criteria. Also, a 16th question was added in which experts ranked the strategies from 1 (best) to 15 (worst).

Data analyses

Consistent with the second round, median and IQD scores were analysed. For the rank question, results for the three different experts groups were analysed separately using mean values. All statistical analyses were conducted using SPSS statistical software (version 15.00, SPSS Inc., Chicago, IL, USA).

Results

First round

The ideation session resulted in various strategies that could be divided into four subcategories: (i) taxes, e.g. healthy food options at a lower VAT rate, (ii) government interference and insurance system, e.g. additional food allowance for low-income groups, (iii) way of offering and presentation, e.g. post with recipes: healthy, easy and cheap, (iv) price and discounts, e.g. healthy food options on special offer (Table 2).

Second round

Kendall’s tau correlation matrix revealed that for most pricing strategies, the eight criteria correlated significantly. However, it also revealed that, except for political feasibility and practical workability in strategy A2, and opportunities for implementation and practical workability in D1, none of the criteria had a correlation> 0.80, indicating that the eight criteria were independent scales. Therefore, all criteria were separately included in analyses.

From these eight criteria, we first looked more specifically at the effectiveness criterion. In total, 15 strategies had an effectiveness median ≥ 3.5 (scale 1–7). Of these strategies, 10 also scored a median ≥ 3.5 on political feasibility, 10 on practical workability, 11 on implementation opportunities, 14 on affordability, 14 on social justice, 12 on consumer acceptance and 10 on industry acceptance. In total, seven strategies scored a median ≥ 3.5 on all eight criteria (Table 2). In contrast with high median scores, we found low consensus scores; all strategies had an IDQ ≥ 2. Strategies with an IQD ≥ 1 and a median ≥ 3.5 on the criterion effectiveness were selected for the third round (Table 2).

Third round

Table 3 shows the outcomes of the third round. In general, higher consensus levels were obtained compared to the second round. With respect to agreement, measures were rated differently on the listed criteria. For example, introducing a sudden price rise in unhealthy food items scored a median of 2 on political feasibility, in contrast to a score of 4 on effectiveness and affordability. In general, median scores were high (78% median ≥ 3.5) and consensus was good (67% IQD ≤ 1). Two strategies had both median scores ≥ 3.5 and IQD scores ≤ 1 on all eight criteria, indicating that experts agreed on the quality of those strategies. These strategies were offering small presents with healthy food items and providing price cuts on healthy food items.

View this table:
Table 3

Results 3rd round. Median (scale 1–7) and IQD scores of pricing strategies outlined by the eight criteria

Political feasibilityPractical workabilityImplementation opportunitiesEffectivenessAffordabilitySocial justiceAcceptance consumersAcceptance trade and industry% IQD ≤ 1 per strategy
Price StrategyMdnIQDaMdnIQDMdnIQDMdnIQDMdnIQDMdnIQDMdnIQDMdnIQD
A1*424242424252614213
A2323231414141323250
B4423141424242424225
C1525151425151515175
C2514141413141514288
C35151414140515151100
C4414241423241503250
C5525152424151505163
D15151514.514251515188
D2213021424132212075
D3515241414151514188
D4514141414151514288
D85151514140515041100
D11323132424141312163
D12323232414142412238
% IQD ≤ 1 per element5367735373738753
  • *For clarification of the strategies see Table 2

  • a: IQD indicates the distance between the 25th and the 75th percentiles

Additionally, experts were asked to rank the strategies. Table 4 shows the results of the overall ranking and those of the separate expert groups. Scores were given from 1 to 15, with a lower score indicating a higher ranking. Overall, the strategy of putting healthy food options on special offer more frequently had the highest rank (mean 5.5), and introducing a sudden price rise of unhealthy food items the lowest (mean 11.4). However, clear differences between expert groups were observed. Contrary to the overall rank of 15, sector B ranked the strategy of a sudden price rise for unhealthy food options in the third place. Also, while offering the healthy option of comparable products for a lower price was ranked in third place by the overall group, this same strategy was ranked in 11th place by sector B. Sector C ranked putting healthy food options on a lower VAT rate in the 10th place, while the overall group ranked this in second place.

View this table:
Table 4

Overall ranks of the pricing strategies and by different groups of expertise

Price strategyRank overall (1–15)MeanRank sector A (Δ)Mean sector ARank sector B (Δ)Mean sector BRank sector C (Δ)Mean sector C
D1*1a5.452 (−1)5.311 (−)5.753 (−2)5.42
A126.271 (+1)4.622 (−)6.5010 (−8)7.92
D436.423 (−)5.8511 (−8)10.001 (+2)4.67
D846.735 (−1)6.925 (−1)8.134 (−)5.58
C156.736 (−1)7.084 (+1)7.635 (−)5.75
D367.4211 (−5)8.1510 (−4)9.502 (+4)5.25
C377.887 (−)7.628 (−1)8.389 (−2)7.83
B487.9410 (−2)8.156 (+2)8.257 (+1)7.50
D1297.978 (+1)7.699 (−)8.3811 (−2)8.00
C5108.094 (+6)6.7714 (−4)10.888 (+2)7.67
C2118.399 (+2)7.9215 (−4)11.006 (+5)7.17
D11129.6112 (−)8.1512 (−)10.3813 (−1)9.17
C4139.7313 (−)10.0013 (−)10.5012 (+1)8.92
A21410.1814 (−)10.467 (+7)8.3814 (−)11.08
D21511.4215 (−)13.463 (+12)7.5015 (−)11.83
  • *For clarification of the strategies see Table 2

  • a: Rank 1 = the best score; rank 15 = the worst score

  • Δ = difference in rank number between the named expert group and overall rank

Discussion

This study resulted in a list of pricing strategies that by a heterogeneous expert panel had been indicated as being promising in stimulating healthier food choices and being feasible for implementation. This result is an essential first step for the future design of pricing strategies. Former studies argued that barriers surrounding pricing strategies may form a main obstacle for implementation. In line with this, we found that experts did have the tendency to overestimate the potential of pricing strategies for which the implementation responsibilities could be placed elsewhere. Nevertheless, our results revealed that several pricing strategies have potential. The strategy with the best prospects was discounting healthier food options more frequently.

Several authors have proposed pricing strategies as a tool in changing dietary behaviour, and several arguments for price incentives are listed.17–20,31,32 Experiments in controlled settings showed that price reductions are effective in changing food purchases.33 Also, studies on fiscal incentives revealed that taxes and subsidies on food may be effective.16,34–36 Based on this, pricing strategies seem a promising intervention tool. Nevertheless, there are a lot of complicating factors surrounding pricing strategies. For example, pricing strategies may (1) distort markets, (2) result in cross elasticity, (3) have regressive effects, (4) cannot be implemented because of different prevailing interests.15,34,37 In order to overcome these barriers, data restricted to the effectiveness of pricing strategies may not be useful.

We found clear differences in the pricing strategies ratings regarding feasibility on the one hand and effectiveness on the other hand. For example, the introduction of a sudden price rise for unhealthy food products was considered to be very effective but scored low on political feasibility and industry acceptance. For the actual implementation of pricing strategies, it is important to take this discrepancy into consideration.31 A second point of attention is that strategies were rated differently among involved sectors, supposedly influenced by implementation responsibilities. We found that the government experts mainly preferred measures that should be performed by the industry (best example: offering the healthy food option of comparable products for a lower price), while the industry experts mainly preferred measures that should be performed by the government (best example: putting healthy food options at a lower VAT rate). It is important to consider this carefully. Promoting a healthy diet is worldwide considered important, but apart from economical conditions in developing countries, the political view of a liberal market and the industrial view of profit making are important competing issues. Due to these financial and political interests, factual interference in the food market is not favoured.38

The strategy that fitted well with issues of conflicting interests was discounting healthy food options more frequently. This strategy was ranked high(est) by all different sectors and was indicated feasible, effective, affordable and acceptable by the industry. This promising character is underlined by marketing research conducted previously, demonstrating substantial effects on purchasing behaviour of temporal price promotions. Price promotions are suggested to have a larger impact than price reductions since consumers tend to buy a product simply because it is on sale.39 This implicates that near constant discounting of different types of healthy food items would be the best option to stimulate more healthy food purchases. Based on interaction process in the ideation session, we suggest that the best way to solve the payment issue of such a strategy is to combine forces of the retail, industry and government sector. All experts in our panel were broadminded towards creative solutions, and losses for merchants may be small since the upgraded sales due to the discounts may account for the lower profit.33

Our Delphi study shows interesting results; however, there are some methodological points of consideration. First, the expert panel may not reflect the true expert opinion in this field. Especially, in the first round, the response rate was low and sampling and identification of experts may have been exposed to subjectivity. However, we managed to compose a sample containing experts from all the important sectors. Experts with high organizational positions were invited, which may have lowered the response rates but also raised the quality of our panel. Furthermore, compared with other Delphi studies, the response rate was acceptable.24 A second point of consideration is that anonymity was provided in the second and third rounds, but not in the first round. As a rule, anonymity is a specific feature of Delphi designs as it protects participants from group pressure or obstruction from talking freely about divergent opinions.40 However, in our study, it was considered relevant that experts from different fields became familiar with important issues in other fields. Previous authors suggested that hearing other point of views may lead to levelling of arguments and higher levels of consensus.21 Next to this, active participation and discussion with other experts may enlarge further cooperation in the actual implementation of pricing strategies, a phenomenon characterizing Delphi studies in general.22

Conclusion

Our results provide a divergent list of pricing strategies that by a carefully selected group of experts had been indicated as being promising in stimulating healthier food choices. Following this study, it is important to learn how to make solid agreements on responsibility and implementation issues. Currently, different authorities do not feel responsible for introducing financial incentives on food. Also it is significant to study consumer perspectives and the effectiveness of the proposed pricing strategies in stimulating healthier food choices. This should include large-scale experiments studying whether consumers would actually buy more healthy foods if this would become more financially attractive.

Funding

This work was supported by a grant from the Netherlands Organization for Health Research and Development (ZonMw), The Hague, The Netherlands, grant number: 50-50105-96-426.

Conflicts of interest: None declared.

Key points

  • Due to competing interests and feasibility problems, the introduction of pricing strategies is complicated. It is essential to explore incentives that are realizable and being approved by different sectors involved. Our study is the first that gives insight in these aspects.

  • This study resulted in a list of pricing strategies that by a carefully selected group of experts had been indicated as being promising in stimulating the healthier food choice and being feasible for implementation. This result is an essential first step for the future design of pricing strategies.

  • Our results reveal that experts did have the tendency to give the highest rates to the pricing strategies for which the implementation responsibilities could be placed elsewhere. This is an important finding, which is essential for future successful intervention development and implementation.

  • We found that, by expert views, constant discounting of different types of healthy food items would be the best option to stimulate more healthy food purchases. Because our study included experts from the industry, retail and government sector, it provides a unique insight in the feasibility aspects of such a strategy.

Acknowledgements

We would like to thank the experts who participated in this study. Furthermore, we would like to thank the Dutch marketing and strategy agency (ISMC) for providing professional support and the location for the ideation session.

References

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