The tipping point: a mathematical model for the profit-driven abandonment of restaurant tipping

The custom of voluntarily tipping for services rendered has gone in and out of fashion in America since its introduction in the 19th century. Restaurant owners that ban tipping in their establishments often claim that social justice drives their decisions, but we show that rational profit-maximization may also justify the decisions. Here, we propose a conceptual model of restaurant competition for staff and customers, and we show that there exists a critical conventional tip rate at which restaurant owners should eliminate tipping to maximize profit. Because the conventional tip rate has been increasing steadily for the last several decades, our model suggests that restaurant owners may abandon tipping en masse when that critical tip rate is reached.Comment: 14 pages, 5 figures, supplementary material include

Metropolitan area growth: a test of export base concepts

Regional economics ; Federal Reserve Bank of St. Louis

Simulating Quantum Mechanics by Non-Contextual Hidden Variables

No physical measurement can be performed with infinite precision. This leaves a loophole in the standard no-go arguments against non-contextual hidden variables. All such arguments rely on choosing special sets of quantum-mechanical observables with measurement outcomes that cannot be simulated non-contextually. As a consequence, these arguments do not exclude the hypothesis that the class of physical measurements in fact corresponds to a dense subset of all theoretically possible measurements with outcomes and quantum probabilities that \emph{can} be recovered from a non-contextual hidden variable model. We show here by explicit construction that there are indeed such non-contextual hidden variable models, both for projection valued and positive operator valued measurements.Comment: 15 pages. Journal version. Only minor typo corrections from last versio

Liquidity and efficiency during unusual market conditions : an analysis of short selling restrictions and expiration-day procedures on the London Stock Exchange

University of Technology Sydney. Faculty of Business.While enhancing market quality has always been an important goal, this challenge has taken on even greater significance with increasing competition between securities markets both nationally and internationally. This thesis examines the influence of several key market design features on the market quality of the London Stock Exchange (LSE). The first issue examined is the impact of regulatory changes to short selling constraints on liquidity and order flow during periods of extreme uncertainty. During the 2008-9 UK emergency temporary short selling ban, restricted stocks experienced lower trading activity, wider spreads, reduced order book depth, and more aggressive trading. The restrictions occurred at a time of extreme uncertainty when price volatility increased and there was more trading activity in the upstairs market. Our findings suggest that limit order trading may be less viable during turbulent times and should interest policymakers concerned with maintaining fair markets during crisis periods. Second, this thesis examines trading conditions during another period of market strain; index derivatives expiration days. Previously unexamined, the LSE employs a unique intraday call auction procedure to minimise expiration-day effects on underlying stocks. Price and volume data is examined around the expiration of FTSE 100 index futures and option contracts to determine the efficacy of the UK approach. Evidence of significant increases in trading volume and abnormal stock returns in the underlying market on expiration days is found. However, the effects are short-lived and small relative to transactions costs, suggesting that use of an intraday call auction mechanism is effective in maintaining a fair and orderly market. The third issue analysed in this thesis is whether current expiration-day procedures give rise to exploitable market efficiencies. Individual stock returns prior to expiration are found to help predict future prices in the short-term. This predictive ability is used to derive trading strategies which are tested under real-world conditions to search for systematic profitable trading opportunities. Although the model forecasts produce higher returns than a passive benchmark, the gains are small after allowing for transaction costs implying that LSE expiration-day procedures foster an efficient market. This thesis has implications for economic efficiency and policy. Together, study of these distinctive market design features of the LSE and their respective impacts on liquidity and market efficiency contributes to an enhanced understanding of optimal market design. Our findings should interest academics and market operators concerned with maintaining fair and efficient markets, particularly during critical trading periods

Cost-effectiveness of physical fitness training for stroke survivors

Background Physical fitness is impaired after stroke, yet fitness training after stroke reduces disability. Several international guidelines recommend that fitness training be incorporated as part of stroke rehabilitation. However, information about cost-effectiveness is limited. Methods A decision tree model was used to estimate the cost-effectiveness of a fitness programme for stroke survivors vs. relaxation (control group). This was based on a published randomised controlled trial, from which evidence about quality of life was used to estimate Quality Adjusted Life Years. Costs were based on the cost of the provision of group fitness classes within local community centres and a cost per Quality Adjusted Life Year was calculated. Results The results of the base case analysis found an incremental cost per Quality Adjusted Life Year of £2,343. Conclusions Physical fitness sessions after stroke are a cost-effective intervention for stroke survivors. This information will help make the case for the development of new services

Decoherence of multi-dimensional entangled coherent states

For entangled states of light both the amount of entanglement and the sensitivity to noise generally increase with the number of photons in the state. The entanglement-sensitivity tradeoff is investigated for a particular set of states, multi-dimensional entangled coherent states. Those states possess an arbitrarily large amount of entanglement $E$ provided the number of photons is at least of order $2^{2E}$. We calculate how fast that entanglement decays due to photon absorption losses and how much entanglement is left. We find that for very small losses the amount of entanglement lost is equal to $2/\log(2)\approx 2.89$ ebits per absorbed photon, irrespective of the amount of pure-state entanglement $E$ one started with. In contrast, for larger losses it tends to be the remaining amount of entanglement that is independent of $E$. This may provide a useful strategy for creating states with a fixed amount of entanglement.Comment: 6 pages, 5 figure

Saccadic latency in amblyopia.

We measured saccadic latencies in a large sample (total n = 459) of individuals with amblyopia or risk factors for amblyopia, e.g., strabismus or anisometropia, and normal control subjects. We presented an easily visible target randomly to the left or right, 3.5° from fixation. The interocular difference in saccadic latency is highly correlated with the interocular difference in LogMAR (Snellen) acuity-as the acuity difference increases, so does the latency difference. Strabismic and strabismic-anisometropic amblyopes have, on average, a larger difference between their eyes in LogMAR acuity than anisometropic amblyopes and thus their interocular latency difference is, on average, significantly larger than anisometropic amblyopes. Despite its relation to LogMAR acuity, the longer latency in strabismic amblyopes cannot be attributed either to poor resolution or to reduced contrast sensitivity, because their interocular differences in grating acuity and in contrast sensitivity are roughly the same as for anisometropic amblyopes. The correlation between LogMAR acuity and saccadic latency arises because of the confluence of two separable effects in the strabismic amblyopic eye-poor letter recognition impairs LogMAR acuity while an intrinsic sluggishness delays reaction time. We speculate that the frequent microsaccades and the accompanying attentional shifts, made while strabismic amblyopes struggle to maintain fixation with their amblyopic eyes, result in all types of reactions being irreducibly delayed

Intra-accumbens baclofen, but not muscimol, increases second order instrumental responding for food reward in rats

Stimulation of either GABA(A) or GABA(B) receptors within the nucleus accumbens shell strongly enhances food intake in rats. However the effects of subtype-selective stimulation of GABA receptors on instrumental responses for food reward are less well characterized. Here we contrast the effects of the GABA(A) receptor agonist muscimol and GABA(B) receptor agonist baclofen on instrumental responding for food using a second order reinforcement schedule. Bilateral intra-accumbens administration of baclofen (220-440 pmol) stimulated responding but a higher dose (660 pmol) induced stereotyped oral behaviour that interfered with responding. Baclofen (220-660 pmol) also stimulated intake of freely available chow. Muscimol (220-660 pmol) was without effect on responding for food on this schedule but did stimulate intake of freely available chow. Unilateral administration of either baclofen or muscimol (220 pmol) induced similar patterns of c-fos immunoreactivity in several hypothalamic sites but differed in its induction in the central nucleus of the amygdala. We conclude that stimulation of GABA(A) or GABA(B) receptors in the nucleus accumbens shell of rats produces clearly distinguishable effects on operant responding for food