Comparison of individual and paired learning for the measurement of retention

Thesis (Ed.M.)--Boston UniversityThe purpose of this study was to measure and compare retention between children working alone and with a partner using S.R.A. (Scientific Research Associates) reading materials. The S.R.A. laboratory is a series of graded reading experiences intended to be used by individual children working alone and at their own rate of speed. Its general purpose is to improve many reading skills but in this study the retention factor will be the only concern

Concentration Levels in the U.S. Advertising and Marketing Services Industry: Myth vs. Reality

This paper analyzes changes in concentration levels in the U.S. Advertising and Marketing Services (A&MS) industry using publicly released data that have been largely ignored in past discussions of the industrial organization of this industry, namely those available from the U.S. Census Bureau's quinquennial Economic Census and the Service Annual Survey. We define the A&MS industry in terms of nine sectors, each of which is represented by a separate 5 digit NAICS category. In so doing, we have sought to redress some of the measurement problems surrounding estimates found in the existing literature. Our main findings are threefold. First, in the case of the core and largest sector, Advertising Agencies, firm level concentration as measured by Herfindahl-Hirschman Index (HHI) increased slightly but remained relatively low from 1977 to 2002. All of the HHI estimates readily satisfied the standard widely used to characterize an industry as "unconcentrated." We find mixed support for the hypotheses that the ranks of mid-sized agencies were depleted by ongoing waves of mergers and acquisitions and resulted in a polarized size structure. The size distributions of agency revenue have become more polarized in the sense that over time they appear more skewed, more dispersed, and exhibit greater inequality. The share of total receipts realized by small agencies fell while that of large agencies rose. However, the position of mid-sized agencies appears to have changed little over the period 1977- 2002, as measured by the shares of agencies and receipts they represent. Second, concentration levels in 1997 and 2002 varied across the nine sectors comprising the A&MS industry, but all were within the range generally considered as indicative of a competitive industry. Third, we developed concentration ratios at the level of holding companies (HC's) and find that the four largest HC's captured between a fifth and a quarter of total revenue from the A&MS industry, a share that remained quite stable over the period, 2002-2006. These estimates are lower by an order of magnitude than estimates often cited in the trade press. Reasons for the discrepancy are discussed.

Costs, Institutional Mobility Barriers, and Market Structure: Advertising Agencies as Multiproduct Firms

What accounts for the diversity and limited concentration that has long characterized the organization of the advertising agency industry? This question is addressed by treating an advertising agency as a multiproduct firm. The firm's product line or service mix is defined in terms of the set of different media categories where an agency places the advertising messages which it creates on behalf of its clients. Evidence is presented indicating that the structure of demand and costs in the advertising agency industry conforms to the conditions that MacDonald and Slivinski (1987) showed were required for an industry to sustain an equilibrium with diversified firms. Building on this framework, we formulate a set of three hypotheses relating to the realization of product-specific scale and scope economies. The first two hypotheses posit that given low fixed costs and minimal entry barriers, both media-specific scale and scope economies are available and can be exploited by relatively small-size agencies. The third hypothesis suggests that large agencies may experience diseconomies of scope as a consequence of excessive diversification induced by two pervasive industry institutional phenomena: (i) 'bundling' of agency services to match client demand for a mix of media advertising; and (ii) 'conflict policy' which prohibits an agency from serving competing accounts and operates as a mobility constraint. Utilizing a multiproduct cost function, we estimate media-specific scale and scope economies for a cross-section of 401 U.S. agencies in 1987. The results obtained support the set of three hypotheses outlined above.

Galactic Escape Speeds in Mirror and Cold Dark Matter Models

The mirror dark matter (MDM) model of Berezhiani et al. has been shown to reproduce observed galactic rotational curves for a variety of spiral galaxies, and has been presented as an alternative to cold dark matter (CDM) models. We investigate possible additional tests involving the properties of stellar orbits, which may be used to discriminate between the two models. We demonstrate that in MDM and CDM models fitted equally well to a galactic rotational curve, one generally expects predictable differences in escape speeds from the disc. The recent radial velocity (RAVE) survey of the Milky Way has pinned down the escape speed from the solar neighbourhood to $v_{esc}=544^{+64}_{-46}$ km s$^{-1}$, placing an additional constraint on dark matter models. We have constructed an MDM model for the Milky Way based on its rotational curve, and find an escape speed that is just consistent with the observed value given the current errors, which lends credence to the viability of the MDM model. The Gaia-ESO spectroscopic survey is expected to lead to an even more precise estimate of the escape speed that will further constrain dark matter models. However, the largest differences in stellar escape speeds between both models are predicted for dark matter dominated dwarf galaxies such as DDO 154, and kinematical studies of such galaxies could prove key in establishing, or abolishing, the validity of the MDM model.Comment: Accepted for publication in the European Physical Journal