Economic Benefits of Bt Maize Maize containing a transgenically expressed toxin originating from Bacillus thuringiensis (Bt maize) is planted across the United States to combat insect herbivory. Non-Bt Maize is also planted alongside Bt maize fields to provide refuges for the insects, which helps to prevent resistance to Bt maize from evolving. Hutchison et al. (p. 222 ; see the Perspective by Tabashnik ) analyzed how Bt maize affected the economic impact of the European corn borer moth in the midwestern United States, as well as its population dynamics. Larval density, a predictor of corn borer population size, has dropped in correlation with the percentage of Bt maize planted. In the highest Bt maize producing state, the positive effects of Bt maize in controlling insect herbivore populations extended to non-Bt maize. Furthermore, the decrease in insect populations demonstrated an overall economic benefit outweighing the overall extra costs associated with planting Bt maize.

The bark beetles Ips pini, I. perroti, and I. grandicollis are sympatric in pine forests of the north-central United States. They share the same limited phloem resource and often coexist within the same host trees. We tested whether phloem resources are partitioned in time and space by measuring spatial and seasonal colonization of logs. Differences among species in flight phenology, development time, voltinism, and spatial colonization patterns within logs reduce, but do not eliminate, species overlap. The bark beetle species share predation by Thanasimus dubius (Cleridae) and Platysoma cylindrica (Histeridae), which exploit pheromone signals for prey location. We employed pheromone traps to test for chemical communication among bark beetle species. Heterospecific signals tend to be deterrents when they are added to conspecific signals but attractants when they are alone, indicating that the communication system can both reduce and increase species overlap in resource use depending upon relative abundance of the species. Deterrence by heterospecific signals is probably a result of selection for minimizing interspecific competition. However, individuals may sometimes benefit from joining aggregations of other species because of (1) predator swamping, (2) improved success in attacking live trees, and (3) location of suitable, recently dead, trees. These benefits should be greatest for males (which locate and colonize host trees before signalling females) and indeed males tended to be more attracted than females by heterospecific signals. Shared resources, shared predators, and heterospecific pheromone communication all contribute to species interactions in this guild of bark beetles, but predicting whether the removal of one species will tend to increase or decrease the abundance of remaining species remains difficult. Species interactions are likely conditional and coexistence is probably promoted by benefits to rare species of multispecies associations.

We compare fees charged by investment banks for conducting IPOs in the United States and Europe. In recent years, the "7% solution," as documented by Chen and Ritter (2000), has become even more prevalent in the United States, and is now the norm for IPOs raising up to $250 million. The same banks dominate both markets, but European IPO fees are roughly three percentage points lower, are much more variable, and have been falling. We review explanations for the gap in spreads and find the evidence consistent with strategic pricing. U.S. issuers could have saved over $1 billion a year by paying European fees.OVER 10 YEARS AGO, Chen and Ritter (2000) documented that IPO issuers in the United States almost always pay a gross spread of exactly 7% of proceeds to the underwriting syndicate for IPOs of between $20 million and $80 million. This evidence on the clustering of fees prompted an investigation by the U.S. Department of Justice, although this was ultimately dropped for lack of evidence of explicit collusion. A class-action antitrust lawsuit was also launched, and was settled privately after a 2007 appeals court decision allowing the claim against the underwriters to proceed. 1 Chen and Ritter cautioned that explicit collusion was unlikely, but concluded that the clustering of fees is consistent with implicit collusion-or "strategic pricing"-on the part of investment bankers. Subsequent papers by Hansen (2001) andTorstila (2003) argue against even implicit collusion. Hansen maintains that the U.S. IPO market is not unduly concentrated and that barriers to entry are low. Torstila points out that there is clustering of IPO fees outside the United States, but at lower levels, and argues that clustering need not be collusive. * Abrahamson, Jenkinson, and Jones are at the Saïd Business School, Oxford University. The authors thank the anonymous referee and the editor (Campbell Harvey) for many valuable comments and suggestions. We also thank the Centre for Corporate Reputation at the Saïd Business School, Oxford University for financial support for this research. 1 The original class-action lawsuit was filed in 1998, alleging fee-fixing by 32 underwriters, over the period 1994 to 1998. Most recently, the case has been pursued by two plaintiffs, one of which bought the right to bring a claim from a company that had conducted an IPO but then become bankrupt, and the other being a group of creditors of another company that had similarly gone public and then become bankrupt. In 2006, the District Court ruled that these plaintiffs were not qualified to pursue the case.In this paper, we first assess whether the "7% solution" still stands in U.S. IPOs. In other cases, where clustering of gross spreads has been identified by researchers, behavior has changed quickly. The findings of Christie, Harris, and Shultz (1994) that NASDAQ market makers systematically avoided setting quotes on the odd eighths were reported in national newspapers on May 25 and 26, 1994. The next day, the use of odd eighths increased sharply and effectiv...

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