Phased-In Tax Cuts and Economic Activity

Phased-in tax reductions are a common feature of tax legislation. This paper uses a dynamic general equilibrium model to quantify the effects of delaying tax cuts. According to the analysis of the model, the phased-in tax cuts of the 2001 tax law substantially reduced employment, output, and investment during the phase-in period. In contrast, the immediate tax cuts of the 2003 tax law provided significant incentives for immediate production and investment. The paper argues that the rules and accounting procedures used by Congress for formulating tax policy have a significant impact in shaping the details of tax policy and led to the phase-ins, sunsets, and temporary tax changes in both the 2001 and 2003 tax laws.Fiscal Policy, Tax Policy

Memory Time

In this issue of Neuron, MacDonald et al. describe hippocampal “time cells” that fire during specific delay periods as rats performed a memory task. Converging results in monkeys suggest that the hippocampus encodes episodes by signaling events in time

A complete record from colonization to extinction reveals density dependence and the importance of winter conditions for a population of the silvery blue, Glaucopsyche lygdamus.

Butterflies in the family Lycaenidac are often the focus of conservation efforts. However, our understanding of lycaenid population dynamics has been limited to relatively few examples of long-term monitoring data that have been reported. Here, factors associated with population regulation are investigated using a complete record of a single population of the silvery blue, Glaucopsyche lygdamus Doubleday (Lepidoptera: Lycaenidae). Adults of G. lygdamus were first observed in an annual grassland near Davis, California, in 1982 and were last seen in 2003. Relationships between inter-annual variation in abundance and climatic variables were examined, accounting for density dependent effects. Significant effects of both negative density dependence and climatic variation were detected, particularly precipitation and temperature during winter months. Variation in precipitation, the strongest predictor of abundance, was associated directly and positively with butterfly abundance in the same year. Winter temperatures had a negative effect in the same year, but had a lagged, positive effect on abundance in the subsequent year. Mechanistic hypotheses are posed that include climatic effects mediated through both larval and adult plant resources

The Final Fate of Binary Neutron Stars: What Happens After the Merger?

The merger of two neutron stars usually produces a remnant with a mass significantly above the single (nonrotating) neutron star maximum mass. In some cases, the remnant will be stabilized against collapse by rapid, differential rotation. MHD-driven angular momentum transport eventually leads to the collapse of the remnant's core, resulting in a black hole surrounded by a massive accretion torus. Here we present simulations of this process. The plausibility of generating short duration gamma ray bursts through this scenario is discussed.Comment: 3 pages. To appear in the Proceedings of the Eleventh Marcel Grossmann Meeting, Berlin, Germany, 23-29 July 2006, World Scientific, Singapore (2007

A novel, rapidly acquired and persistent spatial memory task that induces immediate early gene expression

<p>Abstract</p> <p>Background</p> <p>The Morris water maze task is a hippocampus-dependent learning and memory test that typically takes between 3 days to 2 weeks of training. This task is used to assess spatial learning and induces the expression of genes known to be crucial to learning and memory in the hippocampus. A major caveat in the protocol is the prolonged duration of training, and difficulty of assessing the time during training in which animals have learned the task. We introduce here a condensed version of the task that like traditional water maze tasks, creates lasting hippocampus-dependent spatial cognitive maps and elicits gene expression following learning.</p> <p>Methods</p> <p>This paradigm was designed for rats to quickly acquire a hippocampus-dependent spatial cognitive map and retain this memory for at least 24 hours. To accomplish this, we interspersed visible and hidden training trials, delivering them in a massed fashion so training takes a maximum of 15 minutes. Learning was assessed based on latencies to the platform during each training trial, as well as time spent in the goal quadrant during probe testing 30 minutes and 24 hours after training. Normal rats were compared to two impaired cohorts (rats with fimbria-fornix lesions and rats administered NMDA receptor antagonist (CPP)). To quantitate hippocampal expression of known learning genes, real-time polymerase chain reaction (RT-PCR) was performed on hippocampal cDNA.</p> <p>Results</p> <p>We show that massed training using alternating visible and hidden training trials generates robust short-term working and long-term reference memories in rats. Like the traditional Morris water maze paradigm, this task requires proper hippocampal function, as rats with fimbria-fornix lesions and rats administered CPP fail to learn the spatial component of the task. Furthermore, training in this paradigm elicits hippocampal expression of genes upregulated following learning in a variety of spatial tasks: <it>homer1a, cfos </it>and <it>zif268</it>.</p> <p>Conclusions</p> <p>We introduce here a condensed version of the Morris water maze, which is like a traditional water maze paradigm, in that it is hippocampus-dependent, and elicits hippocampal expression of learning genes. However, this task is administered in 15 minutes and induces spatial memory for at least 24 hours.</p

Stepping Off the Wage Escalator: The Effects of Wage Growth on Equilibrium Employment

This paper emphasizes the role of wage growth in shaping work incentives. It provides an analytical framework for labor supply in the presence of a return to labor market experience and aggregate productivity growth. A key finding of the theory is that there is an interaction between these two forms of wage growth that explains why aggregate productivity growth can affect employment rates in steady state. The model thus speaks to an enduring puzzle in macroeconomics by uncovering a channel from the declines in trend aggregate wage growth that accompanied the productivity slowdown of the 1970s to persistent declines in employment. The paper also shows that the return to experience for high school dropouts has fallen substantially since the 1970s, which further contributes to the secular decline in employment rates. Taken together, the mechanisms identified in the paper can account for all of the increase in nonemployment among white male high school dropouts from 1968 to 2006. For all white males, it accounts for approximately one half of the increase in the aggregate nonemployment rate over the same period.