290,320 research outputs found
Trends in quality-adjusted skill premia in the United States, 1960-2000
This paper presents new evidence that increases in college enrollment lead to a decline in
the average quality of college graduates between 1960 and 2000, resulting in a decrease of 8
percentage points in the college premium. The standard demand and supply framework (Katz
and Murphy, 1992, Card and Lemieux, 2001) can qualitatively account for the trend in the
college and age premia over this period, but the quantitative adjustments that need to be made
to account for changes in quality are substantial. Furthermore, the standard interpretation of
the supply effect can be misleading if the quality of college workers is not controlled for. To
illustrate the importance of these adjustments, we reanalyze the problem studied in Card and
Lemieux (2001), who observe that the rise in the college premium in the 1980s occurred mainly
for young workers, and attribute this to the differential behavior of the supply of skill between
the young and the old. Our results show that changes in quality are as important as changes
in prices to explain the phenomenon they document
Estimating distributions of potential outcomes using local instrumental variables with an application to changes in college enrollment and wage inequality
This paper extends the method of local instrumental variables developed by Heckman and Vyt-
lacil (1999, 2001, 2005) to the estimation of not only means, but also distributions of potential
outcomes. The newly developed method is illustrated by applying it to changes in college enroll-
ment and wage inequality using data from the National Longitudinal Survey of Youth of 1979.
Increases in college enrollment cause changes in the distribution of ability among college and high
school graduates. This paper estimates a semiparametric selection model of schooling and wages to
show that, for fixed skill prices, a 14% increase in college participation (analogous to the increase
observed in the 1980s), reduces the college premium by 12% and increases the 90-10 percentile ratio
among college graduates by 2
Experience in the use of engineering product design principles to extend novice engineer capability
Effect of Plasma Irradiation on films
The effect of plasma irradiation is studied systematically on a 4H polytype
(002) oriented stoichiometric film having compressive residual
stress. Plasma irradiation was found to change the orientation to (110) of the
film at certain moderate irradiation distances. A linear decrease in grain size
and residual stress was observed with decreasing irradiation distance (or
increasing ion energy) consistent with both structural and morphological
observations. The direct optical energy gap was found to increase
linearly at the rate with the compressive stress. The
combined data of present compressive stress and from earlier reported tensile
stress show a consistent trend of change with stress. The
iodine-iodine distance in the unit cell could be responsible for the observed
change in with stress.Comment: 13 pages and 10 fi
Recommended from our members
Gullies on Mars: Origin by snow and ice melting and potential for life based on possible analogs from Devon Island, High Arctic
Gullies on Devon Island, High Arctic, which form by melting of transient surface ice and snow covers and offer morphologic and contextual analogs for gullies reported on Mars are reported to display enhancements in biological activity in contrast to surrounding polar desert terrain
N-Triflylphosphorimidoyl Trichloride: A Versatile Reagent for the Synthesis of Strong Chiral BrĆønsted Acids
A series of strong BrĆønsted acids has been synthesized in high yields using N-triflylphosphorimidoyl trichloride as reagent. The syntheses proceed efficiently with electron-rich, electron-deficient, and sterically hindered substrates
U(1) Gauge Theory of the Hubbard Model : Spin Liquid States and Possible Application to k-(BEDT-TTF)_2 Cu_2 (CN)_3
We formulate a U(1) gauge theory of the Hubbard model in the slave-rotor
representation. From this formalism it is argued that spin liquid phases may
exist near the Mott transition in the Hubbard model on triangular and honeycomb
lattices at half filling. The organic compound k-(BEDT-TTF)_2 Cu_2 (CN)_3 is a
good candidate for the spin liquid state on a triangular lattice. We predict a
highly unusual temperature dependence for the thermal conductivity of this
material.Comment: 5 pages, 2 figures; paper shortened and the phase diagram of
anisotropic triangular lattice correcte
Double-heterostructure GaAs-GaAIAs injection lasers on semi-insulating substrates using carrier crowding
GaAsāGaAlAs doubleāheterostructure lasers were fabricated on semiāinsulating substrates. Laser action based on carrier confinement via the crowding effect has been demonstrated. Laser action takes place in a narrow (10ā20 Ī¼m) region near the edge of the mesa where the current is injected. The threshold current is low and is comparable to that of stripeāgeometry lasers
Reply to "Comment on 'Scalar-tensor gravity coupled to a global monopole and flat rotation curves' "
In Brans-Dicke theory of gravity we explain how the extra constant value in
the formula for rotation velocities of stars in a galactic halo can be obtained
due to the global monopole field. We argue on a few points of the preceding
Comment and discuss improvement of our model.Comment: 4 pages, RevTeX4 fil
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