day of the week effects and asset returns the number of empirical studies using daily stock returns is rapidly increasing researchers generally assume that the distribution of stock returns is identical for all days of the week a convenient statistical assumption but not a necessary condition of market equilibrium nevertheless there are reasons to suspect that the distribution of returns may vary according to the day of the week the most obvious is the impact of weekends on monday s return since monday s return is calculated over three instead of one calender day the mean and variance may well be higher on monday compared with any other daily return perhaps three times as large previous research has examined the daily distribution of stock returns for a monday effect while fama 1965 does not compare daily mean returns he does report that monday s variance is about 20o greater than other daily returns with a traditional distributional assumption regarding the returns on a financial asset specifies that the expected returns are identical for all days of the week contrary to this plausible assumption this paper discovers that the expected returns on common stocks and treasury bills are not constant across days of the week the most notable evidence is for monday s returns where the mean is unusually low or even negative several explanations of the results are investigated but none proves satisfactory aside from documenting significant day of the week effects the implications of the results for tests of market efficiency are examined while market adjusted returns continue to exhibit day of the week effects these effects are no longer concentrated on monday during the last year we have had many conversations with our colleagues throughout the professions we are particularly thankful to the participants at sessions of the western and american finance associations where preliminary versions of this paper were presented special thanks are due to gene fama gailen hite jon ingersoll robert jarrow merton miller clifford smith and rex thompson the expert research assistance of frank rabinovitch and youngsup yun is gratefully acknowledged 1 the list of papers using daily stock returns is too long to name recent examples include charest 1978 dodd 1980 banz 1981 and reinganum 1981

risk allocation and the costs and benefits of public private partnerships we study the agency costs of delegated public service provision focusing on the link between organizational forms and uncertainty at project implementation we consider a dynamic multitask moral hazard environment where the mapping between efiort and performance is ex ante uncertain but new information may come along during operations our analysis points out at the e ciency gains that bundling planning and implementation as under public private partnerships can bring in terms of better project design and lower operational costs bundling also results in increasingly better performance as uncertainty is reduced by growing experience in the sector bundling should instead be viewed with caution when the private sector seeks to radically innovate on public service provision or to introduce new services but lacks the knowledge and expertise to anticipate the impact of the innovative design procedure technology on the cost of operations the compounding of asymmetric information ex post plus moral hazard and renegotiation may generate diseconomies of scope in agency costs which for high operational risk can make unbundling optimal in this context the use of private flnance can help re establishing the beneflt of bundling only if lenders have su cient expertise to help assessing project risks

a day end transaction price anomaly a large mean price change is observed on the last daily nyse transaction this suggests that closing prices may not consistently represent stock values transaction prices are studied to further characterize the day end price rise and to determine whether it is due to any limited subsample of stocks or dates the results indicate that the phenomenon is pervasive over most firms and days some evidence suggests that it is caused by a change in the frequency of ask prices at day end

can tax loss selling explain the january seasonal in stock returns this paper analyzes the tax loss selling hypothesis as an explanation of the january seasonal in stock returns and argues that rational tax loss selling implies little relation between the january seasonal and the long term loss empirical results show that the january seasonal is as strongly related to the long term loss as it is to the short term loss the evidence is inconsistent with a model that explains the january seasonal by optimal tax trading

durable goods monopolists durable goods monopolists face special problems because the sale of their products creates a secondhand market not controlled by the monopolist to the extent the monopolist is able to rent his product rather than sell it or to make binding promises about his future production such problems are ameliorated given the inability to do the above the monopolist is led to producing goods less durable than those produced by either competitive firms or monopolist returns a reverse averch johnson result that monopolist sellers may invest less in fixed costs including plant modernization and research and development than would the renters is shown it is also shown that even though sellers have less monopoly power than renters and nondurable goods monopolists it is possible that the seller will cause a greater deadweight loss than the other types of monopolies

portfolio rebalancing and the turn of the year effect this paper finds that for the 1935 1986 period the market s risk return relation does not have a january seasonal the findings differ from those of other studies due to the use of value weighted rather than equally weighted portfolios inferences are sensitive to the weighting procedure because of the small firm return patterns in january in particular even in those januaries for which the market return is negative small firm returns are positive and they are more positive the higher is beta this is consistent with the portfolio rebalancing explanation of the turn of the year effect since at least 1926 the average return on small firms in january has been unusually high a phenomenon known as the turn of the year effect in this paper we present new evidence regarding the risk return characteristics of small firms in january we find that for small firms there is a positively sloped riskreturn relation in both up and down markets this pattern is difficult to reconcile with the belief that the high return on small firms in january is equilibrium compensation for risk bearing we show how these patterns in small firms returns have led others to conclude that the market s risk return relation has a january seasonal in particular rozeff and kinney 21 and tinic and west 22 23 among others using equally weighted portfolios formed on the basis of historical betas have found a steeper slope for the capm s risk return relation in january than in other months we demonstrate that this pattern exists only for small firms consequently statistical inferences about the risk return relation are heavily dependent upon whether equally weighted or value weighted portfolio returns are used in the estimation we show that for 1935 86 when monthly cross sectional regressions are estimated using value weighted portfolio returns there is no more of a statistically significant difference in the estimated return to risk bearing in january than in the other eleven months of the year the notion that there is a january seasonal in the capm s risk return relation for the us has rapidly become accepted knowledge for example corhay hawawini and michel 6 accept this conclusion and investigate whether other

trading mechanisms and stock returns an empirical investigation this paper examines the effects of the mechanism by which securities are traded on their price behavior we compare the behavior of open to open and close to close returns on nyse stocks given the differences in execution methods applied in the opening and closing transactions opening returns are found to exhibit greater dispersion greater deviations from normality and a more negative and significant autocorrelation pattern than closing returns we study the effects of the bid ask spread and the price adjustment process on the estimated return variances and covariances and discuss the associated biases we conclude that the trading mechanism has a significant effect on stock price behavior

u k financial market returns 1955 2000 we present and analyze new monthly index series for u k financial assets covering equities bonds bills and inflation the data are consistent with the crsp ibbotson series for the united states we use our indices to estimate equity and bond premia and to make international comparisons especially with the united states germany and japan we illustrate potential uses of the new series by investigating stock market seasonality inflation linked bonds real dividend growth rates and the small firm effect while some of our findings resemble u s results we also report differences between u k and u s stock market behavior copyright 2001 by university of chicago press

risk return and equilibrium a revisit this paper reports the results of tests of the major implications of the two parameter capital asset pricing model the findings indicate that the relationship between stock returns and systematic risk contains important nonlinearities during 1935 82 these nonlinearities cannot be ascribed to previously documented anomalies related to firm size or january seasonality moreover the test results appear to be sensitive to the choice of the proxy for the market portfolio

the end of the month as a preferred habitat a test of operational efficiency in the money market this paper argues that an aggregate preferred habitat for investors exists on or about the last day of the calendar month due to standardizations in the nation s payments system resulting in a concentrated flow of funds on this date thus equilibrium yield discounts are predicted for securities maturing on such dates empirical tests on monthly and daily treasury bill data support the principal hypothesis as well as several ancillary hy potheses the results have implications for treasury debt management for the short term cash and debt management practices of businesses and banks and for the empirical esti mation of daily weekly or monthly return premiums on risky securities

measuring corruption in infrastructure evidence from transition and developing countries abstract this paper examines what we can say about the extent and impact of corruption in infrastructure using existing evidence there is evidence that most perceptions measures appear to be very weak proxies for the actual extent of corruption in the infrastructure sector largely but inaccurately measuring petty rather than grand corruption survey evidence is more reliable but limited as a tool for differentiating countries in terms of access to infrastructure finance or appropriate policy models the paper suggests that a focus on bribe payments as the indicator of the costs of corruption in infrastructure may be misplaced

call option pricing and the turn of the year historically common stocks have had larger returns and variability of returns around the turn of the year and january the authors find that call option prices reflect these historical patterns ex ante that is the higher return variability is anticipated and incorporated into the prices of call options whose trade date and expiration date fall on opposite sides of a turn of the year period these results suggest that both the turn of the year and the january phenomena are widely anticipated by financial markets before the fact copyright 1989 by the university of chicago

credible signals of the release of new versions i introduction many products are marketed some time after they have been developed for instance a new smartphone may be developed and tested well before it is available for purchase a new car might be prototyped and driven months before it comes to the market indeed a firm will often have several products concurrently in a development pipeline consumers may know a product is in that pipeline without knowing its progress towards the market because the outcome of such development and testing is not visible to outsiders the firm knows whether it can market a product before consumers do consumers are uninformed about when and if the new product will be marketed to them economists have long recognized that the present demand for durable goods depends on future prospects such as the future price or the introduction of an improved version 1 the existence of such an improved version is often the seller s private information if consumers anticipate a new version some will defer purchases until the new version is available and the seller will face low demand for the present version disclosing the new version is not in a monopoly seller s interest a seller whose good does not have a new version would also like to communicate that fact to consumers while a firm with a successful product innovation can credibly disclose the new version with relative ease a firm that has failed to develop a new product could have great difficulty convincing consumers that the product has no new version in such situations it is important to examine whether prices can inform consumers whether a new version will be marketed in the near future in a recent paper choi et al 2010 developed a model with a risky product development process in which reputation effects allow cheap talk announcements to signal successful product development to consumers an announcement induces consumers to delay or divert purchases to the announcer s coming product which increases the announcer s profit and can improve welfare 2 in their model the announcer and her non innovative rivals supply the original good competitively because of this an announcement does not reduce profit on the current version this paper will focus on markets where the seller has substantial market power before innovating so announcing a successful product development has a cost in terms of current revenue further because we attend to prices as signals this model may also apply to markets where a long run relationship between consumers and firms may not be sustainable another objective of this paper is to examine the welfare effects of mandatory disclosure a government policy mandating disclosure of any new version is an alternative means of informing consumers 3 as long as firms are not willing to lie to the government such a policy would credibly communicate whether a new version of a durable is coming mandatory disclosure would bring about full information as consumers are informed about any improved future version before observing the price of the current version in this paper we explore a two period model of a durable good monopoly in which consumers are initially uninformed about whether there will be a new version of the current good the monopoly seller is privately informed if he will be able to market an improved version in the second period in the first period consumers must decide whether to purchase the good now or wait for an upgraded version they may be able to infer from the price of the current version whether the seller will bring a new version to the market it is important to see first whether prices can serve as signals and second how welfare compares between any signaling outcome and a full information benchmark corresponding to mandatory disclosure we will show that there is a unique equilibrium supported by intuitive beliefs in this equilibrium the seller s private information about an improved version is completely revealed to consumers

on requiring the durable goods monopolist to sell abstract requiring a monopolist to sell its output rather than renting it my lead to beneficial output adjustments or harmful quality adjustments in a durable goods model we show that requiring sales decreases welfare in only a small fraction of cases but it strictly increases welfare in a majority of cases

a further investigation of the weekend effect in stock returns this study uses a longer time period and additional stocks to further investigate the weekend effect we find consistently negative monday returns 1 for the s p composite as early as 1928 2 for exchange traded stocks of firms of all sizes and 3 for actively traded over the counter otc stocks the otc results are based on bid prices and therefore appear to reject specialist related explanations for the 30 individual stocks of the dow jones industrial index the average correlation between friday and monday returns is positive and the highest of all pairs of successive days the latter finding is inconsistent with fairly general measurement error explanations some of the most puzzling empirical findings reported in recent years indicate that the distribution of common stock returns varies by day of the week most notably the average return for monday close friday to close monday is significantly negative cross 3 and french 6 find negative monday returns using the standard and poor s composite index and gibbons and hess 7 find negative monday returns for the 30 individual stocks of the dow jones industrial index 1 this negative monday return or weekend effect has yet to be explained this study undertakes a further investigation of the weekend effect in stock returns we examine additional time periods extending the total period covered to 55 years we examine additional stocks such as those of small low capitalization firms and those traded over the counter in all cases the data exhibit a weekend effect that is at least as strong as that reported in previous studies the study also readdresses potential explanations for the effect such as measurement error but concludes that none of these explanations is satisfactory the first section presents a history of the weekend effect from 1928 through 1982 based on the standard and poor s composite index we essentially double the length of the period beginning in 1953 examined by french 6 the results indicate consistently negative monday returns throughout the 55 year period during much of the 25 year period from 1928 through 1952 the new york stock exchange was open on saturdays so monday s return is then computed from saturday s close to monday s close 2 these returns for one day weekends are consistently negative and not significantly different from the two day weekend

day of the week effect on the paris bourse abstract we present evidence on the day of the week effect on a stock market with a particular settlement procedure the paris bourse a strong and persistent negative return is found on tuesdays a similar result was previously found for japan and australia the settlement procedure is shown to have an effect on the distribution of daily returns consistent with forward pricing theory it cannot explain the negative tuesday return after adjusting for this settlement effect the mean return on mondays is the largest in the week a result at odds with the evidence in the u s a

a new perspective on planned obsolescence automobile manufacturers have long had a policy of introducing annual style changes into their new model cars textbook publishers have a policy of periodically bringing out revised editions of their popular books recently ibm changed the operating system used in its personal computers causing a reduction in the compatibility between its old and new machines if one were to ask the typical man in the street to explain what is happening in these markets he would not hesitate before giving the following answer in economists terminology he would say that for the above firms the incentive to introduce new products that make old units obsolete is too high i e the firms have an incentive to practice planned obsolescence of course just as is true for the man in the street economists have also long observed and commented on the speed with which new products are introduced for example galbraith 1958 suggests that the annual model changes of automobile manufacturers are socially wasteful while fisher griliches and kaysen 1962 provide empirical estimates of the costs of these changes there have also been numerous theoretical attempts to model the idea of planned obsolescence or the related idea of killing off the market for secondhand goods but most of these models have in fact considered the choice a monopolist faces concerning how much durability to build initially into his product rather than the monopolist s incentive to introduce new versions of his product over time 1 in this paper i consider planned obsolescence from the standpoint of a firm that can change the nature of what it sells and show that the man in the street is in fact correct in many settings the incentive for a durable goods monopolist to introduce new products that make old units obsolete will be above that which is socially optimal

licensing information goods abstract a significant amount of research on patent licensing and the diffusion of knowledge is organized around static frameworks of analysis patent holders however may face a dynamic problem namely the intertemporal consistency problem of the durable goods monopolist that is induced by durability on the demand side licensing practices such as exclusive licensing contracts and most favored customer clauses allow patentees to solve or mitigate this dynamic consistency problem there are situations however where these practices are not possible either due to the nature of the patent the case of information goods or due to compulsory patenting laws we study the effects of the intertemporal consistency problem on patent licensing in these situations relative to the existing literature we obtain the following main results i all of the firms that remain in the industry will be using the innovation ii royalty licensing may be superior to fixed fee or auction licensing from the licensor s point of view iii social welfare and consumer surplus may be lower than when the patent holder can commit not to make additional sales iv even for non drastic innovations the price of the good that is produced may be lower than the competitive price corresponding to the initial situation before the innovation was discovered

new findings regarding day of the week returns over trading and non trading periods a note this paper decomposes daily close to close returns into trading day and non trading day returns we discover that all of the average negative returns from friday close to monday close documented in the literature for stock market indexes occurs during the non trading period from friday close to monday open in addition average trading day returns open to close are identical for all days of the week january firm size turn of the year anomalies are shown to be interrelated with day of the week returns

risk return and equilibrium an extension this study extends a recent empirical reexamination of the risk ret urn relationship by examining the possibility that an omitted size re lationship may account for the anomalous results h levy s generaliz ed capital asset pricing model provides the theoretical basis for incorporating the impact of firm size on expected return by examining the relative importance of unsystematic risk in pricing closely held securities compared to pricing widely held securities in so doing the empirical analysis also provides a test of an implication of the generalized capital asset pricing model two methodologies are used t o test the hypotheses empirically the results indicate that even thou gh size has a significant impact on the risk return relationship it apparently does not account for the anomalous results this implicati on is consistent under both methodologies copyright 1988 by the university of chicago

stock market seasonals and prespecified multifactor pricing relations despite nonstationarities in the factor betas and factor prices of the chen roll ross 1986 multifactor model investors are rewarded for bearing risks associated with the change in expected inflation and industrial production in non january months however variations in these factors have opposite influences on stock prices these findings may partially explain why several recent studies fail to detect a significant non january risk premium in the stock market but this evidence is only suggestive since theoretical and statistical difficulties prevent precise interpretations of specific pricing relations in the chen roll ross model

optimal stock trading with personal taxes implications for prices and the abnormal january returns abstract the tax law confers upon the investor a timing option to realize capital losses and defer capital gains with the tax rate on long term gains and losses being about half the short term rate the law provides a second timing option to realize losses short term and gains long term if at all our theory and simulation over the 1962 1977 period establish that taxable investors should realize long term gains in high variance stocks and repurchase stock in order to realize potential future losses short term tax trading does not explain the small firm anomaly but predicts a seasonal pattern in trading volume which maps into a seasonal pattern in stock prices the january anomaly only if investors are irrational or ignorant of the price seasonality

is the efficient market hypothesis day of the week dependent evidence from the banking sector in this article we propose a new hypothesis that the efficient market hypothesis is day of the week dependent we apply the test to firms belonging to the banking sector and listed on the nyse we find significant evidence that the efficient market hypothesis is day of the week dependent overall for only 62 of firms the unit root null hypothesis is rejected on all the five trading days we also discover that when investors do not account for unit root properties in devising trading strategies they obtain spurious profits

time varying volatilities and calculation of the weighted implied standard deviation rogalski tinic have reported a monthly pattern in ex post stock return variances that differs between small and large market capitalization firms maloney rogalski find that option prices reflect these monthly patterns ex ante this study extends maloney rogalski s work by devising an expiration specific weighted implied standard deviation wisd it is found that i the monthly patterns in one month wisds are basically similar to the monthly patterns in ex post variances detected by rogalski tinic for both large and small size firms and ii use of expiration specific wisds as opposed to standard composite wisds results in improved performance of option pricing models

idiosyncrasies in australian petrol price behaviour evidence of seasonalities it has been argued that there are certain idiosyncrasies in australian petrol price behaviour to the extent that these idiosyncrasies result in large magnitude differences in petrol prices they may be exploited by consumers to significantly reduce their household expenditure on the product similarly such seasonalities may influence retailers in their purchase and storage decision the objective of this paper is to test for seasonalities in the australian retail petrol market the approach adopted is similar to that for determining calendar anomalies as documented in the financial and commodity markets literature we find that a monthly seasonal effect is pronounced with petrol prices lower in the months of february may and highest in july and august a day of the week effect is also apparent and is manifest in all petrol prices for capital cities adelaide brisbane melbourne and sydney across various years however the half month effect as is common in stock returns is not observed moreover contrary to popular belief that petrol prices are higher surrounding holidays no evidence of the holiday effect is found in brisbane and melbourne petrol prices also have some relationship to the mood of consumers as proxied using weather conditions this is not observed in adelaide and sydney

durable goods market structure and the incentives to innovate a commonly cited finding in the innovation literature is that a monopoly tends to innovate too little this paper demonstrates that a monopoly may devote more resources to innovation than is socially optimal if it produces a durable good this possibility occurs because durability creates new innovation incentives once an initial stock of a durable good has been produced the monopoly faces a residual demand for the good innovation may allow the monopoly to more profitably exploit this residual demand and this ability may lead the monopoly to devote more resources to innovation than is socially optimal copyright 1987 by the review of economic studies limited

a note on welfare in the durable goods monopoly depending upon the shape of the rental demand curve facing a durable goods monopolist social welfare may be raised or lowered by requiring the monopolist to sell rather than rent its output indeed the equilibrium under rentals may pareto dominate the equilibrium under sales copyright 1989 by the london school of economics and political science

privatisation discontent and utility reform in latin america abstract privatisation faces strong and increasingly popular opposition in latin america this paper uses individual data on social attitudes socioeconomic status and demographic information from three waves of latinobarometro surveys 1998 2000 and 2002 in 17 countries to study the role of privatisation of utilities and its distributional impact we find that disagreement with privatisation is most likely when the respondent is on a low to middle income and when it involves a high proportion of public services such as water and electricity this complements recent empirical research that points to distributional concerns in the implementation of privatisation in latin america particularly because of inadequate regulation of utilities

efficiency of experimental security markets with insider information an application of rational expectations models the study reports on the ability of competing models of market information integration and dissemination to explain the behavior of simple laboratory markets for a one priced security returns to the security depended upon a randomly drawn state of nature some agents insiders whose identity was unknown to other agents knew the state before the markets opened with replication of market conditions the predictions of a fully revealing rational expectations model are relatively accurate prices adjusted immediately to near rational expectations prices profits of insiders were virtually indistinguishable from non insiders and efficiency levels converged to near 100 percent

are seasonal anomalies real a ninety year perspective in recent years there has been a proliferation of empirical studies documenting unexpected or anomalous regularities in security rates of return in addition to the widely studied relation between firm size and rate of return 1 these include seasonal regularities related to the time of the day harris 1986 the day of the week see ball and bowers 1986 cross 1973 french 1980 gibbons and hess 1981 jaffe and westerfield 1985 keim and stambaugh 1984 and lakonishok and levi 1982 the time of the month ariel 1987 and the turn of the year see haugen and lakonishok 1988 jones pearce and wilson 1987 lakonishok

the week end effect in common stock returns the international evidence this paper examines the daily stock market returns for four foreign countries we find a so called week end effect in each country in addition the lowest mean returns for the japanese and australian stock markets occur on tuesday the remainder of the paper answers four questions are seasonal patterns in foreign stock markets independent of those previously reported in the u s do japan and australia exhibit a seasonal one day out of phase due to different time zones do settlement procedures across countries bias week end effects does the seasonal pattern in foreign exchange offset the week end effect in stocks for americans investing overseas some of the most anomalous empirical findings in finance are associated with the sample distributions of daily common stock returns cross 1 french 2 gibbons and hess 3 and keim and stambaugh 4 have documented that the average return on friday is abnormally high and the average return on monday is abnormally low to our knowledge this so called day of the week effect or week end effect has yet to be explained because this anomaly has been reported primarily for u s stock returns it is appropriate to investigate whether similar results occur for other countries positive findings would strongly support the proposition that the weekly seasonal effect is a general world wide phenomenon rather than the result of a special type of institutional arrangement in the u s to shed more light on this proposition our paper examines stock market returns in the u k japan canada and australia since we find a week end effect in each country we can examine a set of interesting questions for example are these seasonals independent of the previously reported seasonal in the u s due to different time zones do far eastern countries exhibit a seasonal one day out of phase do different settlement procedures across countries influence weekend effects does the seasonal in foreign exchange fluctuations see mcfarland pettit and sung 7 and levi 6 offset the week end effect in stock market returns for americans investing overseas

the january size effect anomaly or risk mismeasurement 1986 the january size effect anomaly or risk mismeasurement financial analysts journal vol 42 no 6 pp 63 70

calendar anomalies abnormal returns at calendar turning points 1988 calendar anomalies abnormal returns at calendar turning points financial analysts journal vol 44 no 6 pp 28 39

a transaction data study of weekly and intradaily patterns in stock returns abstract weekly and intradaily patterns in common stock prices are examined using transaction data for large firms negative monday close to close returns accrue between the friday close and the monday open for smaller firms they accrue primarily during the monday trading day for all firms significant weekday differences in intraday returns accrue during the first 45 minutes after the market opens on monday mornings prices drop while on the other weekday mornings they rise otherwise the pattern of intraday returns is similar on all weekdays most notable is an increase in prices on the last trade of the day

the italian stock market efficiency and calendar anomalies abstract after describing the various concepts of efficiency information valuation full insurance and functional with special reference to the italian stock market the paper analyzes the impact of particular dates and periods of the civil year and stock exchange calendars on stock price changes to test the existence of information inefficiencies the analysis is based on the milan stock exchange s mib storico stock index with reference to the period 2 january 1975 22 august 1989 the events tested for systematic anomalies include weekend and public holidays the end of the calendar and stock exchange months and the end of the year the results obtained are in line with those found for the u s market with evidence of anomalous changes though not all are stable over time

playing the turn of the year effect with index futures the turn of the year effect is a well documented stock market phenomenon in which low capitalization small stocks receive relatively higher returns than high capitalization big stocks on the last trading day of december and the first 8 trading days of january the difference in returns during this period is of the order of 10 strategies for buying and selling these small stocks may be profitable but may also incur large transaction costs that eliminate most or all of the projected gains in this paper we show a preferable way to invest in order to exploit this anomaly use a futures spread that is long in the small stocks and short in the big stocks the optimal investment which uses a modification of the capital growth criterion is large and has a substantial expected gain with minimal risk we have used this analysis successfully in managing investment accounts

the dynamics of corruption with the ratchet effect this paper provides a simple model of corruption dynamics with the ratchet effect as in shleifer and vishny 1993 we consider the sale of government property entry permit by government officials as the prototype of corruption activities in a dynamic version of the shleifer vishny model corrupt officials have ex post the incentive to price discriminate entrepreneurs based on the entry decisions made in an earlier period we show that the inability of government officials to commit to future money demands induces the ratchet effect in that entrepreneurs have incentives to delay entry in order to receive a discount in the permit price later the ex post opportunism erodes the official s extortion power and reduces his revenues from selling permits even though the dynamic setting leaves the corrupt official with less extortion power we cannot rule out the possibility that the official s ability to apply dynamic discrimination decreases the intertemporal aggregate social welfare we also explore the effect of the official s tenure stability on the extent of corruption this allows us to identify circumstances under which the often observed practice of job rotation can help mitigate corruption