Introduction à l économie appliquée

Transcription

1 Introduction à l économie appliquée Chapitre II Les contours de l analyse empirique Où l on montre que l économie empirique est plus que l empirique de l économie. En partant de l analyse des addictions, des constats empiriques, des défis théoriques et du fondement des politiques de santé contre le risque du tabac, on découvre comment se construit la démarche empirique Automne 2018 Université de Tours - A. Chassagnon

2 Copyright L étude analysée est celle de Fabrice Etilé, (INRA et PSE) Intitulée Introduction to the Economics of Smoking, qu il a présenté en 2009 dans le cours "Health, Income and Well-Being" une des références : A Theory of Rational Addiction publié par Gary S. Becker and Kevin M. Murphy, JPE 1988

3 Plan du Cours : les étapes d une étude empirique 0 Le sujet 1 La/les motivations 2 La/les premières analyses des faits 3 La/les représentations théoriques 4 Les data utilisés 5 Les recommandations de politique économique

4 0. Le sujet Le tabac, et, plus généralement, l addiction

5 1. Les motivations

6 According to the WHO (1999), "by 2030, tobacco is expected to be the single biggest cause of death worldwide, accounting for about 10 million deaths per year". Yet, this risk factor, as many other health-related lifestyle behaviours, is amenable to prevention because it is (partly) under the individual control. Etilé (PSE) () Economics of Smoking March / 58

7 Où l on fait la différence entre qualitatif et quantitatif According to the WHO (1999), "by 2030, tobacco is expected to be the single biggest cause of death worldwide, accounting for about 10 million deaths per year". Yet, this risk factor, as many other health-related lifestyle behaviours, is amenable to prevention because it is (partly) under the individual control. l importance du sujet est relatée par le superlatif biggest et aussi par le fait que le facteur de risque considéré est en partie sous contrôle (under control) Cependant, on doit noter que cette appréciation est qualitative, qu elle appelle une appréciation qualitative (graphique, tableau statistique, contexte particulier)

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11 de quel choix parle-t on? En économie, lorsque l on commence à étudier un sujet, on doit tout de suite se demander quels sont les choix économiques qui sont en jeu, quelle est la rationalité, quels sont les canaux économiques (les prix, l information qu on doit mettre en oeuvre. Ici, il s agit du choix de personnes qui sont addictes. Est-ce un choix rationnel ou pas? Que se passe-il quand ces personnes arrêtent : est-ce l effet d un changement de préférence, d une force extérieure (matérielle, morale) ou simplement l effet de changement de prix?

12 Défi théorique Doit-on opposer un consommateur rationnel d un consommateur emprunt d addiction Rational consumers maximize utility from stable preferences as they try to anticipate the future consequences of their choices. Addictions would seem to be the antithesis of rational behavior. Does an alcoholic or heroin user maximize or weigh the future? D après Becker et Muryphy (JPE, 1988) la réponse est négative : we claim that addictions, even strong ones, are usually rational in the sense of involving forward-looking maximization with stable preferences. Our claim is even stronger : a rational frame- work permits new insights into addictive behavior.

13 2. Les faits

14 Mesure des faits On doit toujours distinguer entre plusieurs mesures : les mesures en quantité : ici le nombre de décès dûs au tabac les mesures comptables : ici, ce que coûte le tabac les mesures en bien-être : Ici, la prise en compte de l utilité des fumeurs, de leur désir et du plaisir qu ils ont à fumer, et la désutilité de leur entourage.

15 For France, the MILDT reports by Kopp and Fenoglio (2000, 2004) provide interesting numbers. Etilé (PSE) () Economics of Smoking March / 58

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21 Important milestones in public health policies: In the 50 s, rst piece of epidemiological evidence that smoking is implicated in lung cancer. 1964: U.S. Surgeon General s warning about the e ect of smoking on health. Since then, anti-smoking policies in many developed countries have progressively included several of the following elements: incentives-based policies: tax hikes and smoking bans. information-based policies: restrictions on cigarette advertising; general information campaigns (mass-media counter-advertising); targeted prevention campaigns (at schools, for pregnant women, for individuals su ering from chronic diseases...). supply-regulation policies: standardisation of the quality (tar and nicotine levels) and selling restrictions. Etilé (PSE) () Economics of Smoking March / 58

22 For France: the Veil law: limits cigarette advertising to newspapers and magazines; severe restrictions on the use of promotional materials (especially during sport events); packs must display sanitary messages ("L abus est dangereux" + tar and nicotine %); restrictions on cigarette smoking in some public places; propose targeted information campaigns at school and at the army.(during the military service) the Evin law: advertising is almost entirely banned; new limits on levels of tar and nicotine; smoking bans is prohibited in a number of public places; tobacco prices are removed from the computation of the Consumer Price Index =) strong price increases selling restrictions to less than 16-years-old are strengthened smoking bans are extended to all public places (including bars, restaurants, night-clubs). Etilé (PSE) () Economics of Smoking March / 58

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24 Questions about price policies: What is their empirical e ect on smoking behaviours? Do economists have something to say about addictive behaviours? "Should" they not be inelastic to prices? What should be their objective? i.e. optimal tax level? Etilé (PSE) () Economics of Smoking March / 58

25 3. Représentation théorique

26 Définition de l addiction Definition A good is potentially addictive if increases in past consumption raise current consumption. Traduction : U = U(c t, y t, S t ) Dans la prise en compte de la consommation de bien addictifs, on devra aussi prendre en compte le fait que ces biens addictifs ont un effet sur la productivité d un agent, sur son potentiel de création de richesse dans le futur.

27 Becker, G.S. et Murphy, K.M. [1988], "A Theory of Rational Addiction", Journal of Political Economy 96 (4), Etilé (PSE) () Economics of Smoking March / 58

28 Before the 1980s, many economists thought that smoking, and more generally addictive behaviours, were inelastic to prices: the addict does not react to economic incentives... Becker and Murphy s model attempts to show that most features of addictive behaviours can be predicted by a rational choice model. Etilé (PSE) () Economics of Smoking March / 58

29 Basic assumptions: Information is perfect about: the future health consequences of smoking. the addictiveness of smoking + rational habit formation. The individual is time-consistent: exponential discounting. Etilé (PSE) () Economics of Smoking March / 58

30 Time is discrete: t Two goods: cigarette: c t with price p t numeraire: y t Two constraints: accumulation of a "stock of consumption" (habit): S t = (1 d)s t 1 + c t budget constraint: 1 t (1+r ) t (p t c t + y t ) = 1 t (1+r ) t w(h t ) + A 0 where H is the health capital. Etilé (PSE) () Economics of Smoking March / 58

31 Taken together these assumptions mean that the utility function can be rewritten as: with: U/ c > 0, 2 U/ c 2 < 0. u t = U(c t, S t, y t ) U/ S < 0, 2 H/ S 2 < 0: in the terminology of Stigler and Becker (1977), smoking is a "bad" habit. For good habits: U/ S > 0 2 U/ c S > 0 Etilé (PSE) () Economics of Smoking March / 58

32 rational addiction In our theory of rational addiction, "rational" means that individuals maximize utility consistently over time, and a good is potentially ad- dictive if increases in past consumption raise current consumption. We show that steady-state consumption of addictive goods is unstable when the degree of addiction is strong, that is, when the complemen- tarity between past and current consumption is strong. Unstable steady states are a major tool in our analysis of addictive behavior. Consumption rises over time when above unstable steadystate levels, and it falls over time, perhaps until abstention, when below unstable steady states.

33 Addiction Addictions require interaction between a person and a good. Obviously, cigarettes and heroin are more addictive than sweaters and sherbet. Yet not all smokers and heroin users become addicted. We show that, other things the same, individuals who discount the future heavily are more likely to become addicted. The level of incomes, temporary stressful events that stimulate the demand for addictive goods, and the level and path of prices also affect the likelihood of becoming addicted.

34 Permanent changes in prices of addictive goods may have a modest short-run effect on the consumption of addictive goods. This could be the source of a general perception that addicts do not respond much to changes in price. However, we show that the long-run demand for addictive goods tends to be more elastic than the demand for nonaddictive goods.

35 Anticipated future increases in price reduce current consumption of addictive goods because their consumption at different moments of time are complements. This implies that temporary changes in the price of an addictive good have smaller effects on current consumption than (compensated) permanent changes.

36 Strong addictions to smoking, drinking, and drug use are usually broken only by going cold turkey, that is, by abrupt withdrawal. The need for cold turkey may suggest a weak will or other forms of lessthan-rational behavior. Yet we show that cold turkey is consistent with rational behavior. Indeed, rational persons end strong addictions only with rapid and sometimes discontinuous reductions in consumption.

37 t 1 (1+r ) (p t t c t + y t ) = t Max fct,y t,t=0,...,+ g β t U(c t, S t, y t ) 1 (1+r ) t w(s t ) + A 0 S t = (1 d)s t 1 + c t, S 0 given t Etilé (PSE) () Economics of Smoking March / 58

38 As in the consumer s weight control problem, using the F.O.C., we get: U c (t) = λp t β τ τ>t t S U S (τ) τ {z } c {z} t where λ is the marginal utility of money. + λ τ>t 1 (1+r ) τ w t S (τ) {z } {z} As smoking has direct (hedonic) and indirect (budget constraint) negative consequences on well-being, the full price of smoking is higher than its market price. _ S τ c t + Etilé (PSE) () Economics of Smoking March / 58

39 To investigate the dynamics of smoking, assume for simplicity that: d = 1 =) S t = c t 1 U(c, S, y) = a cc 2 c2 + a SS 2 S 2 + a c c + a S S + a cs cs + a y y. Quadratic preferences, with a y, a c, a cs > 0; a cc, a SS, a S < 0. w S = 0 Then, the F.O.C. yields the following dynamic equation: c t = λ a cc +βa SS p t {z } θ p <0 a cs a cc +βa SS {z } θ l >0 c t 1 β a cs a cc +βa SS c t+1 {z } θ f =βθ l >0 a c +βa S a cc βa cs {z } θ 0 Etilé (PSE) () Economics of Smoking March / 58

40 Steady-state (if p t = p) c = θ pp+θ 0 1 θ l θ f Assuming that θ l + θ f < 1, we have c > 0 i θ p p + θ 0 > 0 () a c > λp βa S i.e. U c > λp βu S for c = 0: the marginal utility of the rst cigarette is positive. Etilé (PSE) () Economics of Smoking March / 58

41 Stability x t = c t c =) x t+1 = 1 βθ l x t 1 β x t 1 Caracteristic equation: µ 2 1 βθ l µ + 1 β = 0 Two real solutions µ 1 and µ 2 if 4βθ 2 l < 1 : µ 1 = 1+p 1 2βθ l 4βθ 2 l > 0 and p µ 2 = 1 1 4βθ 2 l 2βθ l > 0 And then: c t = c + αµ t 1 + βµt 2 : convergence and stability (when α and β 6= 0) i jµ 1 j, jµ 2 j < 1 q This requires that 1 4βθ 2 l < 2βθ l 1 hence β > (1/2θ l ) and β > (1 θ l ) /θ l as well as β < 1/(4θ 2 l ) and β < 1 But β < 1 then implies that θ l > 1/2 (using β > (1/2θ l ) or β > (1 θ l ) /θ l ) and β > (1/2θ l ) and β < 1/(4θ 2 l ) is possible only if 1/(4θ 2 l ) > (1/2θ l ) i.e. θ l < 1/2 : contradiction implying µ 1 > 1 As a consequence, one must necessary have α = 0 and β = c 0 c and stability requires only that: β < (1/2θ l ), (1 θ l ) /θ l, 1/(4θ 2 l ).Note that β < (1 θ l ) /θ l () θ l + θ f < 1. Etilé (PSE) () Economics of Smoking March / 58

42 Optimal policy: c t = µ 2 c t 1 + c (1 µ 2 ) c t 1 and c t are positively related because µ 2 > 0 : there is "adjacent complementarity". Becker and Murphy consider that addiction is caracterised by α cs > 0 and adjacent complementarity. Etilé (PSE) () Economics of Smoking March / 58

43 c t c t =S t c* c t =μ 2 S t +c*(1 μ 2 ) S t =c t 1 Etilé (PSE) () Economics of Smoking March / 58

44 With more complex preferences: stable and unstable steady-states. In a more general setting, it can be shown that adjacent complementarity is more likely when the depreciation d is higher, the discount factor β decreases, α cs increases and α ss is not too negative. (1 β) (( β + 2d)α cs > α SS ). Heterogeneity in the initial risk of becoming an addict is due to (ad hoc) heterogeneity in c 0 "Cold-turkey" (sevrage brutal) when shocks on the optimal policy curve f (e.g. c decreases when p increases) Etilé (PSE) () Economics of Smoking March / 58

45 c t c t =ds t c* 1 c t =f(s t ) c* 2 S 1? S t Etilé (PSE) () Economics of Smoking March / 58

46 Short-term unanticipated price e ect: θ p Long-term price e ect: θ p /(1 θ l θ f ) > θ p Change in p t+1 anticipated at t will have an e ect on c t Etilé (PSE) () Economics of Smoking March / 58

47 Criticism : Information is perfect, no need for information campaigns; One just has to internalise the social cost through taxes. Answer by Orphanidès and Zervos (1995) 3 assumptions: Two types of consumer: those at risk for the health and addiction e ects of smoking (er = 1) and the others (er = 0) The consumer does not know a priori his type. He is a bayesian learner. There is a probability of experimenting the risk, which is the product of the probability of being of the risky type, and the probability of a binomial shock (eπ t = 1). The latter - Π(S t ) - is increasing in S t U(c t, S t, y t ) = u(c t, y t ) + er eπ t v(s t ) with v0 < 0. EU(c t, S t, y t ) = u(c t, y t ) + Pr(er = 1jpast events)π(s t )v(s t ) with v0 < 0. Etilé (PSE) () Economics of Smoking March / 58

48 Story (prediction of OZ model): Believing that for her there is almost no risk (i.e. Pr(er = 1jpast events) close to 0), whereas in reality er = 1, because she experiments no adverse e ects (value of the shock=0), the consumer becomes addict, in the sense that S t increases, and reinforces her belief that er = 0. Then, there is a shock eπ t = 1, and she discovers that she is indeed at risk... but too late: S t is too high and she is addicted - rational regret ex post. Does this model provide support to information-based policies: on the one hand, such policies inform the consumer on Π(S t ), but on the other hand, how could we inform individuals (especially teenagers) on their idiosyncratic risk (and how to detect it?) =) this might however be a justi cation for implementing a precautionary principle. Etilé (PSE) () Economics of Smoking March / 58