John Kim

Physician Fees and Procedure Intensity: the Case of Cesarean Delivery

While there is a large literature investigating the response of treatment intensity to Medicare reimbursement differentials, there is much less work on this question for the Medicaid program. The answers for Medicare may not apply in the Medicaid context, since a smaller share of a physicians patients will be Medicaid insured, so that income effects from fee changes may be dominated by substitution effects. We investigate the effect of Medicaid fee differentials on the use of cesarean delivery over the period 1988-1992. We find, in contrast to the backward-bending supply curve implied by the Medicare literature, that larger fee differentials between cesarean and normal childbirth for the Medicaid program leads to higher cesarean delivery rates. In particular, we find that the lower fee differentials between cesarean and normal childbirth under the Medicaid program than under private insurance can explain between one half and three-quarters of the difference between Medicaid and private cesarean delivery rates. Our results suggest that Medicaid reimbursement reductions can cause real reductions in the intensity with which Medicaid patients are treated.

On the lower central series of an associative algebra

Abstract For an associative algebra A, define its lower central series L 0 ( A ) = A , L i ( A ) = [ A , L i − 1 ( A ) ] , and the corresponding quotients B i ( A ) = L i ( A ) / L i + 1 ( A ) . In this paper, we study the structure of B i ( A n ) for a free algebra A n . We construct a basis for B 2 ( A n ) and determine the structure of B 3 ( A 2 ) and B 4 ( A 2 ) . In Appendix A, we study the structure of B 2 ( A ) for any associative algebra A over C .

The incidence game chromatic number of paths and subgraphs of wheels

The incidence game chromatic number was introduced to unify the ideas of the incidence coloring number and the game chromatic number. We determine the exact incidence game chromatic number of large paths and give a correct proof of a result stated by Andres [S.D. Andres, The incidence game chromatic number, Discrete Appl. Math. 157 (2009) 1980-1987] concerning the exact incidence game chromatic number of large wheels.

Decoding Reed–Muller Codes over Product Sets

We give a polynomial time algorithm to decode multivariate polynomial codes of degree d up to half their minimum distance, when the evaluation points are an arbitrary product set Sm, for every d < |S|. Previously known algorithms can achieve this only if the set S has some very special algebraic structure, or if the degree d is significantly smaller than |S|. We also give a near-linear time randomized algorithm, which is based on tools from list-decoding, to decode these codes from nearly half their minimum distance, provided d < (1− ǫ)|S| for constant ǫ > 0. Our result gives an m-dimensional generalization of the well known decoding algorithms for ReedSolomon codes, and can be viewed as giving an algorithmic version of the Schwartz-Zippel lemma.

A Cauchy-Davenport theorem for linear maps

We prove a version of the Cauchy-Davenport theorem for general linear maps. For subsets A, B of the finite field

On universal Lie nilpotent associative algebras

mathbb{F}_p

Cauchy-Davenport Theorem for linear maps: Simplification and Extension

Fp, the classical Cauchy-Davenport theorem gives a lower bound for the size of the sumset A + B in terms of the sizes of the sets A and B. Our theorem considers a general linear map