Individual Financial Decisions in Retirement Saving Plans and The Provision of Resources for Retirement

Proposals for mandatory private saving accounts differ in the degree of investment discretion that they provide to individual savers, and in their provisions for annuitization of accumulated assets. With respect to investment choices, some argue that individuals must be prevented from investing too conservatively, and earning low returns over their accumulation period, while others argue that individuals should be protected from recklessly investing their retirement assets. With respect to annuitization, there is concern that individuals might not choose annuities and would thereby expose themselves to a risk of outliving their assets in a privatized system. This paper draws on the existing experience with 401(k) plans and other defined contribution pension plans to provide evidence on each of these issues. We find that the share of 401(k) plan assets held in corporate equities has increased substantially in recent years. We are only able to provide limited evidence on participant asset management, since many 401(k) plans have limited options in this regard. We do find, however, that a participant's education and income levels are related to asset allocation decisions, with less educated and lower income participants less inclined to invest in equity securities. We also analyze a unique data base on TIAA-CREF participants and find several attributes of annuitization behavior that seem inconsistent with standard behavior in the lifecycle model.

Diffuse radio emission in MACS J0025.4−-1222: the effect of a major merger on bulk separation of ICM components

Mergers of galaxy clusters are among the most energetic events in the Universe. These events have significant impact on the intra-cluster medium, depositing vast amounts of energy - often in the form of shocks - as well as heavily influencing the properties of the constituent galaxy population. Many clusters have been shown to host large-scale diffuse radio emission, known variously as radio haloes and relics. These sources arise as a result of electron (re-)acceleration in cluster-scale magnetic fields, although the processes by which this occurs are still poorly understood. We present new, deep radio observations of the high-redshift galaxy cluster MACS J0025.4$-$1222, taken with the GMRT at 325 MHz, as well as new analysis of all archival $Chandra$ X-ray observations. We aim to investigate the potential of diffuse radio emission and categorise the radio population of this cluster, which has only been covered previously by shallow radio surveys. We produce low-resolution maps of MACS J0025.4$-$1222 through a combination of uv-tapering and subtracting the compact source population. Radial surface brightness and mass profiles are derived from the $Chandra$ data. We also derive a 2D map of the ICM temperature. For the first time, two sources of diffuse radio emission are detected in MACS J0025.4$-$1222, on linear scales of several hundred kpc. Given the redshift of the cluster and the assumed cosmology, these sources appear to be consistent with established trends in power scaling relations for radio relics. The X-ray temperature map presents evidence of an asymmetric temperature profile and tentative identification of a temperature jump associated with one relic. We classify the pair of diffuse radio sources in this cluster as a pair of radio relics, given their consistency with scaling relations, location toward the cluster outskirts, and the available X-ray data.Comment: 20 pages, 15 figures, accepted for publication in A&

Ultrafast and octave-spanning optical nonlinearities from strongly phase-mismatched cascaded interactions

Cascaded nonlinearities have attracted much interest, but ultrafast applications have been seriously hampered by the simultaneous requirements of being near phase-matching and having ultrafast femtosecond response times. Here we show that in strongly phase-mismatched nonlinear frequency conversion crystals the pump pulse can experience a large and extremely broadband self-defocusing cascaded Kerr-like nonlinearity. The large cascaded nonlinearity is ensured through interaction with the largest quadratic tensor element in the crystal, and the strong phase-mismatch ensures an ultrafast nonlinear response with an octave-spanning bandwidth. We verify this experimentally by showing few-cycle soliton compression with noncritical cascaded second-harmonic generation: Energetic 47 fs infrared pulses are compressed in a just 1-mm long bulk lithium niobate crystal to 17 fs (under 4 optical cycles) with 80% efficiency, and upon further propagation an octave-spanning supercontinuum is observed. Such ultrafast cascading is expected to occur for a broad range of pump wavelengths spanning the near- and mid-IR using standard nonlinear crystals.Comment: resubmitted, revised version, accepted for Phys. Rev. Let

The Drawdown of Personal Retirement Assets

How households draw down the balances that they accumulate in retirement saving accounts such as 401(k) plans and Individual Retirement Accounts can have an important effect on the contribution of these accounts to retirement income security. This paper presents evidence on the pattern of withdrawals at different ages. We find a relatively modest rate of withdrawals prior to the age at which households are required to take minimum required distributions. Only seven percent of PRA-owning households between the ages of 60 and 69 take annual distributions of more than ten percent of their PRA balance, and only 18 percent of PRA households in this age group make any withdrawals in a typical year. The rate of distributions rises sharply after age 70 1/2, when minimum distributions are required. The proportion of PRA-owning households making a withdrawal jumps to over 60 percent by age 71, and crosses 70 percent a few years later. On average, households age 60 to 69 with PRA accounts withdraw only about two percent of their account balances each year, considerably less than the rate of return on account balances during our sample period. Even at older ages--after the required minimum distribution age--the percentage of balances withdrawn remains at about five percent.

Recent Progress in Heavy Quark Physics

Some of the recent progress in heavy quark physics is reviewed. Special attention is paid to inclusive methods for determining Vub and factorization in nonleptonic B decays. Theoretical predictions for top-antitop production near threshold are also discussed.Comment: talk given at 2001 Lepton Photon Meeting, 10 pages, 5 figure