Stochastic Models of Implied Volatility Surfaces

We propose a market–based approach to the modelling of implied volatility, in which the implied volatility surface is directly used as the state variable to describe the joint evolution of market prices of options and their underlying asset. We model the evolution of an implied volatility surface by representing it as a randomly fluctuating surface driven by a finite number of orthogonal random factors. Our approach is based on a Karhunen–Loeve decomposition of the daily variations of implied volatilities obtained from market data on SP500 and DAX options.
We illustrate how this approach extends and improves the accuracy of the well–known 'sticky moneyness' rule used by option traders for updating implied volatilities. Our approach gives a justification for the use of 'Vegas' for measuring volatility risk and provides a decomposition of volatility risk as a sum of independent contributions from empirically identifiable factors.
(J.E.L.: G130, C14, C31).     

Endogenous cartel formation: Experimental evidence

In a Bertrand-oligopoly experiment, firms choose whether or not to engage in cartel-like communication and, if so, they may get fined by a cartel authority. We find that the four-firm industries form cartels more often than the duopolies because they gain less from a hysteresis effect after cartel disruption.     

Distributional effects of social security reforms: The case of France

This paper assesses the impact of two social security reforms using a calibrated, dynamic life cycle model. It quantifies the long‐run distributional impact of two sets of reforms in France: (1) the 2013 reform of Prime Minister Ayrault, which modified the parameters of a defined benefit (DB) plan, and (2) a hypothetical reform that changes the system to a notional defined contribution (NDC) plan, similar to that in Italy. First, on aggregate welfare, the Ayrault reform and the hypothetical switch to NDC yield contrasting results. The Ayrault reform improves aggregate welfare, which is not the case for the NDC reform. Welfare comparisons are made with respect to the “benchmark economy,” where increases in life expectancy occur and are dealt with only through a higher contribution rate. Second, both reforms yield unequal distributions of welfare changes, with low‐skill workers on the losing end. Under the Ayrault reform, low‐skill workers delay retirement by two years, to age 62. Under NDC reform, pensions for low‐skill workers fall substantially as inequalities during the work life translate directly into inequalities in pensions. The switch to an NDC scheme leads to a more unequal society in terms of asset and welfare distribution.     

Volatility of volatility is (also) rough

Using high-frequency data for major volatility indexes, we compute the volatility of volatility and show that its logarithm follows a fractional Brownian motion with Hurst parameter smaller than 1/2 thereby extending to the volatility asset class the recent findings obtained for the equity index markets. The results confirm that the volatility of volatility is a rough process and it possesses the long memory property. We also show that the correlation between the volatility and the volatility of volatility is positive, consistent with observations in the volatility option market. Lastly, a robustness check using volatility futures confirms the findings.     

Economic burden of hypoglycemia: Utilization of emergency department and outpatient services in the United States (2005–2009)

Objective: To estimate the economic burden of hypoglycemia on the healthcare system at the national level in the US between the years of 2005–2009.

Methods: This study analyzed the National Hospital Ambulatory Medical Care Survey (NHAMCS), including emergency department (ED) and outpatient department (OPD) components, and the National Ambulatory Medical Care Survey (NAMCS). The annual rates of ED and OPD visits associated with hypoglycemia were reported. Subsequent medical services after disposition were studied. The unit cost of specific medical service was estimated from the Medical Expenditure Panel Survey (MEPS). All annualized costs were adjusted to US 2009 dollars. We also estimated the rates of injury and ambulance use incurring within a visit for hypoglycemia.

Results: The total direct medical cost of hypoglycemia was estimated as $3.49 billion in 2005 and decreased gradually to $1.84 billion in 2009. The declining trend was correlated with hospital admissions from ED, which decreased from 170 665 in 2005 to 71,751 in 2009. Consequently, the estimated annual expenditure of hospitalization for hypoglycemia from ED declined over time by more than half ($2.90 billion in 2005, $1.25 billion in 2009). Injury was reported among 9.5% of the ED visits for hypoglycemia. Ambulances were used among 58% of the ED visits for hypoglycemia.

Conclusion: Hypoglycemia poses a significant burden on the healthcare system; however, annual direct medical cost of severe hypoglycemia in the US decreased over the 5 years studied, which is attributable to tremendous decrease in need of hospitalization following an ED visit.     

Spend as I say,not as I do: Children,families and household consumption in different socio‐economic contexts

This article aims at contributing to a body of work about children and families by exploring the importance of socio‐economic context and social capital for understanding the ways in which money is perceived, obtained and used by children. Alleged contrasts in terms of money management, consumption priorities and postponement of gratification, especially among middle and working classes, have already been debated. It seems thus relevant to investigate if these presumable contrasts apply to children and why. Do children from different socio‐economic contexts reveal the traits that have been attributed to their households? To this end, a mixed methods research project was developed involving 245 children attending different primary schools in Portugal—one private school targeted at upper class children and one state‐sponsored school located in a working‐class area. The results revealed significant differences by school and household typology.     

Innovations in return transmission and performance comparison between the five biggest Euro area stock markets

This article presents an empirical analysis of integration and performance of the five biggest stock markets of the Euro area: France, Germany, Holland, Italy and Spain. This empirical analysis begins with the estimation of an EMU market model with time-varying beta coefficients, which is the basis for the subsequent estimation of the transmission of innovations and volatility between those markets. The present article compares the performance of those stock markets measured by time-varying Treynor ratios. Those ratios support the creation of a portfolio which explores the performance differences between those markets. The capability of this portfolio to exploit those performance differences is subject to evaluation by comparison with a benchmark represented by an equally weighted portfolio.     

Directed technical change and environmental quality

Portuguese Economic Journal - We propose a directed technical change model with two sectors, clean and dirty, to analyze the impact of the degree of substitutability between sectors and the degree...