Do Public Ph.D.-Granting Economics Departments Invert Salaries?

This study analyzes a unique data set containing current salary and detailed job history information on a sample of 902 individuals drawn from 43 public U.S. Ph.D.-granting departments of economics. An analysis of current salaries by academic rank shows that 25% of Assistant Professors earn more that 50% of Associate Professors and 25% of Associate Professors earn more than 25% of Full Professors. Regression analysis suggests that salary inversion is most likely to exist between Associate and Assistant Professors and is more prevalent in lower ranked programs.Salary Inversion

The Inversion of the Land Gradient in the Inner City of Haifa, Israel

While suburbanization and decentralization are familiar concepts in urban economics, there is a possibility that land gradients will not simply flatten over time, but actually invert themselves. This would mean that the traditional CBD or downtown ceases to act as the pinnacle or nucleus of the land/housing pricing function within the metropolitan area. Such a possibility has been noted in the theoretical literature and has been demonstrated empirically in a few cases. Such an urban ‘‘inversion’’ is shown to have occurred in Haifa, Israel. Beginning in the 1960s, the stock of privately-owned cars grew in Israel at one of the most rapid rates ever seen in any industrial country, with relatively little growth in transportation infrastructure.

Non-Nudgable Subgroups of Permutations

Motivated by a problem from behavioral economics, we study subgroups of permutation groups that have a certain strong symmetry. Given a fixed permutation, consider the set of all permutations with disjoint inversion sets. The group is called non-nudgable, if the cardinality of this set always remains the same when replacing the initial permutation with its inverse. It is called nudgable otherwise. We show that all full permutation groups, standard dihedral groups, half of the alternating groups, and any abelian subgroup are non-nudgable. In the right probabilistic sense, it is thus quite likely that a randomly generated subgroup is non-nudgable. However, the other half of the alternating groups are nudgable. We also construct a smallest possible nudgable group, a 6-element subgroup of the permutation group on 4 elements.Comment: new version contains some simplifications and extension

A note on the Taylor series expansions for multivariate characteristics of classical risk processes.

The series expansion introduced by Frey and Schmidt (1996) [Taylor Series expansion for multivariate characteristics of classical risk processes. Insurance: Mathematics and Economics 18, 1–12.] constitutes an original approach in approximating multivariate characteristics of classical ruin processes, specially ruin probabilities within finit time with certain surplus prior to ruin and severity of ruin. This approach can be considered alternative to inversion of Laplace transforms for particular claim size distributions [Gerber, H., Goovaerts, M., Kaas, R., 1987. On the probability and severity of ruin. ASTIN Bulletin 17(2), 151–163; Dufresne, F., Gerber, H., 1988a. The probability and severity of ruin for combinations of exponential claim amount distributions and their translations. Insurance: Mathematics and Economics 7, 75–80; Dufresne, F., Gerber, H., 1988b. The surpluses immediately before and at ruin, and the amount of the claim causing ruin. Insurance: Mathematics and Economics 7, 193–199.] or discretization of the claim size and time [Dickson, C., 1989. Recursive calculation of the probability and severity of ruin. Insurance: Mathematics and Economics 8, 145–148; Dickson, C., Waters, H., 1992. The probability and severity of ruin in finit and infinit time. ASTIN Bulletin 22(2), 177–190; Dickson, C., 1993. On the distribution of the claim causing ruin. Insurance: Mathematics and Economics 12, 143–154.] applying the so-called Panjer’s recursive algorithm [Panjer, H.H., 1981. Recursive calculation of a family of compound distributions. ASTIN Bulletin 12, 22–26.]. We will prove that the recursive relation involved in the calculations of the the nth derivative with respect to – average number of claims in the time unit – of the multivariate finit time ruin probability (developed in the original paper by Frey and Schmidt (1996) can be simplified The cited simplificatio leads to a substantial reduction in the number of multiple integrals used in the calculations and makes the series expansion approach more appealing for practical implementationFinite time ruin probability; Surplus prior to ruin; Severity of ruin; Series expansion; Recursive methods;

Non-inversion tillage in organic arable cropping

The opportunities for using an non-inversion tillage (NI) approach in organic systems has not been well investigated by research and what research has been done has not perhaps been sufficiently long-term. The benefits of the system in terms of the economics of establishment and the improvement in soil quality make the system attractive, but it is a system that will take some time to get established and is one that will require the farmer to “hold his nerve” as grass weed, perennial weed burdens and slug predation may increase in the early years of implementation. In conventional systems and the POB work yields have reported to drop when implementing an NI system. This is before some of the benefits of a better quality soil are seen, but in the work done by Dr Michael Brandt in an organic system no yield drop was experienced. This was also the case for Danish work done by Per Schonning. Phosphate (P) and Nitrate (N) losses can be reduced as soil structure improves and becomes more stable. Better water ingress into the soil will reduce run-off and sediment and P loss and better water retention in the soil structure will reduce leaching potential. This is perhaps particularly the case at the time that the ley phase of a rotation is broken when greatest risks of N leaching occurs particularly if this coincides with significant rainfall

A Nonlinear Super-Exponential Rational Model of Speculative Financial Bubbles

Keeping a basic tenet of economic theory, rational expectations, we model the nonlinear positive feedback between agents in the stock market as an interplay between nonlinearity and multiplicative noise. The derived hyperbolic stochastic finite-time singularity formula transforms a Gaussian white noise into a rich time series possessing all the stylized facts of empirical prices, as well as accelerated speculative bubbles preceding crashes. We use the formula to invert the two years of price history prior to the recent crash on the Nasdaq (april 2000) and prior to the crash in the Hong Kong market associated with the Asian crisis in early 1994. These complex price dynamics are captured using only one exponent controlling the explosion, the variance and mean of the underlying random walk. This offers a new and powerful detection tool of speculative bubbles and herding behavior.Comment: Latex document of 24 pages including 5 eps figure