Reddit’s self-organised bull runs

The shares of GameStop rallied in January after discussions on the social media site Reddit led to a wave of buying of the videogame and consumer electronics retailer’s stock. Valentina Semenova and Julian Winkler study the implication of the use of trading apps and forum discussions among retail investors and write that it is unlikely that this new `modus operandi’ will simply disappear. They say it is important for researchers and policymakers to get ahead of the curve. A delay to a critical assessment of retail investor herding threatens to destabilise markets further

Bringing AI into the Classroom: Designing Smart Personal Assistants as Learning Tutors

Despite a growing body of research about the design and use of Smart Personal Assistants like Amazon’s Alexa, little is known about their ability to be learning tutors. New emerging ecosystems empower educators to develop their own agents without deep technical knowledge. The objective of our study is to find and validate a general set of design principles that educators can use to design their own agents. Using a design science research approach, we present requirements from students and educators as well as IS and education theory. Next, we formulate design principles and evaluate them with a focus group before we instantiate our artifact in an everyday learning environment. The findings of this short paper indicate that the design principles and corresponding artifact are able to significantly improve learning outcomes. The completed work aims to develop a nascent design theory for designing Smart Personal Assistants as learning tutors

Managing fundamentals versus preferences: Re-balancing portfolios and stock returns

What can granular data on investor holdings tell us about stock price variation? I model the growth rate of a portfolio manager's holdings based on evolving asset fundamentals by including demand for asset-specific characteristics in a portfolio optimisation function. Alongside changes in asset characteristics, the manager re-allocates wealth according to evolving preferences. This introduces memory into the portfolio management problem, as past investments inform the choice for new allocations. Using the model, I decompose the growth rate of mutual fund holdings by the effect of i) changing stock characteristics, ii) new preferences, and iii) mean reversion in latent demand. I nest these estimated components, by aggregating holding growth rates by the fund's total net assets, into an expression for stock price growth. I find that changing preferences explain at least as much variation in stock prices as changes in fundamentals. This demonstrates the importance of studying heterogeneity in investor preferences, and their evolution, in furthering our understanding of stock market phenomena

Why is productivity slowing down?

The recent decline in aggregate labor productivity growth in leading economies has been widely described as a puzzle, even a paradox, leading to extensive research into possible explanations. Our review confirms the magnitude of the slowdown and finds that it is largely driven by a decline in total factor productivity and capital deepening. Disaggregation reveals that a significant part of the slowdown is due to sectors that experienced the large benefits from ICTs in the previous period, and that an increasing gap between frontier and laggard firms suggests slower technology diffusion and increasing misallocation of factors. We evaluate explanations that attempt to reconcile the paradox of slowing productivity growth and technological change, including mismeasurement, implementation lags for technologies, and creative destruction processes

Coupled Al/Si and O/N order/disorder in BaYb[Si4–xAlxOxN7–x]sialon

The fractions of aluminium, [Al]/[Al + Si], and oxygen, [O]/[O + N], in crystallographically distinct sites of BaYb[Si4–xAlxOxN7–x] oxonitridoaluminosilicate (space group P63mc, No. 186) were refined based on the results of neutron powder diffraction for a synthetic sample with the composition of x = 2.2(2) and simulated as functions of temperature for the compositions x = 2 and x = 2.3 using a combination of static lattice energy calculations (SLEC) and Monte Carlo simulations. The SLEC calcu lations have been performed on a set of 800 structures differing in the distribution of Al/Si and O/N within the 2 × 2 × 2 supercell containing 36 formula units of BaYb[Si4–xAlxOxN7–x]. The SLEC were based on a transferable set of empirical interatomic potentials developed within the present study. The static lattice energies of these structures have been expanded in the basis set of pair-wise ordering energies and on-site chemical potentials. The ordering energies and the chemical potentials have been used to calculate the configuration energies of the oxonitridoaluminosilicates (so-called sialons) using a Monte Carlo algorithm. The simulations suggest that Al and O are distributed unevenly over two non-equivalent T(Si/Al) and three L(N/O) sites, respectively, and the distribution shows strong dependence both on the temperature and the composition. Both simulated samples exhibit order/disorder transitions in the temperature range 500–1000 K to phases with partial long-range order below these temperatures. Above the transition temperatures the Si/Al and N/O distributions are affected by short-range ordering. The predicted site occupancies are in a qualitative agreement with the neutron diffraction results

Reddit's self-organised bull runs: Social contagion and asset prices

This paper develops an empirical and theoretical case for how `hype' among retail investors can drive large asset fluctuations. We use the dataset of discussions on WallStreetBets (WSB), an online investor forum with over nine million followers as of April 2021, to show how excitement about trading opportunities can ripple through an investor community with large market impacts. This paper finds empirical evidence of psychological contagion among retail investors by exploiting differences in stock price fluctuations and discussion intensity. We show that asset discussions on WSB are self-perpetuating: an initial set of investors attracts a larger and larger group of excited followers. Sentiments about future stock performance also spread from one individual to the next, net of any fundamental price movements. Leveraging these findings, we develop a model for how social contagion impacts prices. The proposed model and simulations show that social contagion has a destabilizing effect on markets. Finally, we establish a causal relationship between WSB activity and financial markets using an instrumental variable approach

Activity-composition relations in the system CaCO3-MgCO3 predicted from static structure energy calculations and Monte Carlo simulations

Thermodynamic mixing properties and subsolidus phase relations of the rhombohedral carbonate system, (1 - x) CaCO3 - x MgCO3, were modelled in the temperature range of 623-2023 K with static structure energy calculations based on well-parameterised empirical interatomic potentials. Relaxed static structure energies of a large set of randomly varied structures in a 4 x 4 x 1 supercell of R3c calcite (a = 19.952A , c = 17.061A ) were calculated with the General Utility Lattice Program (GULP). These energies were cluster expanded in a basis set of 12 pair-wise effective interactions. Temperature-dependent enthalpies of mixing were calculated by the Monte Carlo method. Free energies of mixing were obtained by thermodynamic integration of the Monte Carlo results. The calculated phase diagram is in good agreement with experimental phase boundaries