The Impact of “Rollover” Contracts on Switching Costs in the UK Voice Market : Evidence from Disaggregate Customer Billing Data

In February 2008, British Telecommunications (BT) introduced automatically renewing, or “rollover”, contracts into the UK market for fixed-voice telephone service. These contracts included a 12-month Minimum Contract Period (MCP) with associated Early Termination Charges (ETCs). Unless customers opted out, at the end of the 12 months they would automatically be rolled over into a new MCP and face new ETCs if they later wished to leave BT. Using a unique, disaggregate, customer billing dataset, we measure the impact of rollover contracts on BT customers’ decision to switch to another provider. We find that, controlling for the effects of tenure, broadband purchase, price discounts, and self-selection, rollover households switch after their first MCP 34.8% (54.8%) less than comparable customers on standard plans (fixed-term contracts). These imply rollover contracts induce switching costs on the order of 33.0% of the monthly price of the average BT fixed-voice telephone service. This raises significant concerns about the competitive effects of such contracts n media and telecommunications markets.

Path-integral solution of the one-dimensional Dirac quantum cellular automaton

Quantum cellular automata have been recently considered as a fundamental approach to quantum field theory, resorting to a precise automaton, linear in the field, for the Dirac equation in one dimension. In such linear case a quantum automaton is isomorphic to a quantum walk, and a convenient formulation can be given in terms of transition matrices, leading to a new kind of discrete path integral that we solve analytically in terms of Jacobi polynomials versus the arbitrary mass parameter.Comment: 5 page

Path-sum solution of the Weyl Quantum Walk in 3+1 dimensions

We consider the Weyl quantum walk in 3+1 dimensions, that is a discrete-time walk describing a particle with two internal degrees of freedom moving on a Cayley graph of the group $\mathbb Z^3$, that in an appropriate regime evolves according to Weyl's equation. The Weyl quantum walk was recently derived as the unique unitary evolution on a Cayley graph of $\mathbb Z^3$ that is homogeneous and isotropic. The general solution of the quantum walk evolution is provided here in the position representation, by the analytical expression of the propagator, i.e. transition amplitude from a node of the graph to another node in a finite number of steps. The quantum nature of the walk manifests itself in the interference of the paths on the graph joining the given nodes. The solution is based on the binary encoding of the admissible paths on the graph and on the semigroup structure of the walk transition matrices.Comment: 13 page

Solutions of a two-particle interacting quantum walk

We study the solutions of the interacting Fermionic cellular automaton introduced in Ref. [Phys Rev A 97, 032132 (2018)]. The automaton is the analogue of the Thirring model with both space and time discrete. We present a derivation of the two-particles solutions of the automaton, which exploits the symmetries of the evolution operator. In the two-particles sector, the evolution operator is given by the sequence of two steps, the first one corresponding to a unitary interaction activated by two-particle excitation at the same site, and the second one to two independent one-dimensional Dirac quantum walks. The interaction step can be regarded as the discrete-time version of the interacting term of some Hamiltonian integrable system, such as the Hubbard or the Thirring model. The present automaton exhibits scattering solutions with nontrivial momentum transfer, jumping between different regions of the Brillouin zone that can be interpreted as Fermion-doubled particles, in stark contrast with the customary momentum-exchange of the one dimensional Hamiltonian systems. A further difference compared to the Hamiltonian model is that there exist bound states for every value of the total momentum, and even for vanishing coupling constant. As a complement to the analytical derivations we show numerical simulations of the interacting evolution.Comment: 16 pages, 6 figure

The impact of "rollover" contracts on switching costs in the UK voice market : evidence from disaggregate customer billing data

In February 2008, British Telecommunications (BT) introduced automatically renewing, or “rollover”, contracts into the UK market for fixed-voice telephone service. These contracts included a 12-month Minimum Contract Period (MCP) with associated Early Termination Charges (ETCs). Unless customers opted out, at the end of the 12 months they would automatically be rolled over into a new MCP and face new ETCs if they later wished to leave BT. Using a unique, disaggregate, customer billing dataset, we measure the impact of rollover contracts on BT customers’ decision to switch to another provider. We find that, controlling for the effects of tenure, broadband purchase, price discounts, and self-selection, rollover households switch after their first MCP 34.8% (54.8%) less than comparable customers on standard plans (fixed-term contracts). These imply rollover contracts induce switching costs on the order of 33.0% of the monthly price of the average BT fixed-voice telephone service. This raises significant concerns about the competitive effects of such contracts in media and telecommunications markets

Endogenous product choice : a progress report

Empirical models of differentiated product demand are widely used by both academics and practitioners. While these methods treat carefully the potential endogeneity of price, until recently they have assumed the number and characteristics of the products offered by firms are exogenous. This paper presents a progress report on an ongoing research agenda to address this issue. First, it summarizes how the appropriate choice of “orthogonal” instruments can yield consistent estimates of own and cross-price elasticities in the presence of endogenous product characteristics. Second, it summarizes how to measure “quality markups” and the welfare consequences of endogenous product quality in U.S. cable television markets. Related papers and extensions to consider multiple product characteristics and dynamics are also discussed

The socioeconomic determinants and consequences of women\u27s body mass

The goal of this dissertation is to quantitatively account for the negative relationship between body mass and socioeconomic status observed among women in the U.S. Almost 1 out of 3 white women in the U.S. are currently obese, and data from the National Longitudinal Survey of Youth 1979 (NLSY79) show that, at age 30, obese women have completed almost 1 fewer school grade, are less likely to participate in the labor market, and if they work they have wages that are lower by 17%; they are more likely never to have been married and, if they are married, their spouses have earnings that are lower by 27%. I interpret these facts taking into consideration that not only body mass may affect labor- and marriage-market opportunities but also (a) behavioral factors, potentially influenced by schooling attainment and family income, play a key role in the accumulation of body weight; and (b) women may be heterogeneous in terms of their propensity to gain weight on the one hand and labor- and marriage-market endowments on the other hand. To this end, I specify and estimate a dynamic model in which (a) wage and spousal income offers, as well as the arrival probability of marriage offers, depend on body mass; and (b) women make decisions about their body mass, labor market participation, and marital status over the life cycle. I exploit the estimated model to quantify the consequences of women\u27s body mass in the labor and marriage markets and answer the following questions: (a) How responsive is body mass behavior to labor- and marriage-market incentives? (b) What fraction of the cross-sectional variation in body mass is explained by characteristics formed prior to leaving school? (c) What is the effect of schooling attainment on body mass and through which pathways does this effect unfold over the life cycle? (d) How effective in preventing adult obesity would be policies aimed at eliminating excess weight at the time of school leaving?

The socioeconomic determinants and consequences of women\u27s body mass

The goal of this dissertation is to quantitatively account for the negative relationship between body mass and socioeconomic status observed among women in the U.S. Almost 1 out of 3 white women in the U.S. are currently obese, and data from the National Longitudinal Survey of Youth 1979 (NLSY79) show that, at age 30, obese women have completed almost 1 fewer school grade, are less likely to participate in the labor market, and if they work they have wages that are lower by 17%; they are more likely never to have been married and, if they are married, their spouses have earnings that are lower by 27%. I interpret these facts taking into consideration that not only body mass may affect labor- and marriage-market opportunities but also (a) behavioral factors, potentially influenced by schooling attainment and family income, play a key role in the accumulation of body weight; and (b) women may be heterogeneous in terms of their propensity to gain weight on the one hand and labor- and marriage-market endowments on the other hand. To this end, I specify and estimate a dynamic model in which (a) wage and spousal income offers, as well as the arrival probability of marriage offers, depend on body mass; and (b) women make decisions about their body mass, labor market participation, and marital status over the life cycle. I exploit the estimated model to quantify the consequences of women\u27s body mass in the labor and marriage markets and answer the following questions: (a) How responsive is body mass behavior to labor- and marriage-market incentives? (b) What fraction of the cross-sectional variation in body mass is explained by characteristics formed prior to leaving school? (c) What is the effect of schooling attainment on body mass and through which pathways does this effect unfold over the life cycle? (d) How effective in preventing adult obesity would be policies aimed at eliminating excess weight at the time of school leaving?