Tom Zimmermann

Beta1-Adrenoceptor Polymorphism Predicts Flecainide Action in Patients with Atrial Fibrillation

Background Antiarrhythmic action of flecainide is based on sodium channel blockade. Beta1-adrenoceptor (β1AR) activation induces sodium channel inhibition, too. The aim of the present study was to evaluate the impact of different β1AR genotypes on antiarrhythmic action of flecainide in patients with structural heart disease and atrial fibrillation. Methodology/Principal Findings In 145 subjects, 87 with atrial fibrillation, genotyping was performed to identify the individual β1AR Arg389Gly and Ser49Gly polymorphism. Resting heart rate during atrial fibrillation and success of flecainide-induced cardioversion were correlated with β1AR genotype. The overall cardioversion rate with flecainide was 39%. The Arg389Arg genotype was associated with the highest cardioversion rate (55.5%; OR 3.30; 95% CI; 1.34–8.13; pu200a=u200a0.003) compared to patients with Arg389Gly (29.5%; OR 0.44; 95% CI; 0.18–1.06; pu200a=u200a0.066) and Gly389Gly (14%; OR 0.24; 95% CI 0.03–2.07; pu200a=u200a0.17) variants. The single Ser49Gly polymorphism did not influence the conversion rate. In combination, patients with Arg389Gly-Ser49Gly genotype displayed the lowest conversion rate with 20.8% (OR 0.31; 95% CI; 0.10–0.93; pu200a=u200a0.03). In patients with Arg389Arg variants the heart rate during atrial fibrillation was significantly higher (110±2.7 bpm; pu200a=u200a0.03 vs. other variants) compared to Arg389Gly (104.8±2.4 bpm) and Gly389Gly (96.9±5.8 bpm) carriers. The Arg389Gly-Ser49Gly genotype was more common in patients with atrial fibrillation compared to patients without atrial fibrillation (27.6% vs. 5.2%; HR 6.98; 95% CI; 1.99–24.46; p<0.001). Conclusions The β1AR Arg389Arg genotype is associated with increased flecainide potency and higher heart rate during atrial fibrillation. The Arg389Gly-Ser49Gly genotype might be of predictive value for atrial fibrillation.

FRACTAL ASPECTS OF INTERSTELLAR CLOUDS

Interstellar matter consisting of gas and dust shows structures which appear to have self-similar projected shapes, similar to the properties of terrestrial clouds. Moreover, the completely different physics in these interstellar clouds reveals several additional self-similar/fractal aspects which are investigated by extensive astronomical observations, aiming especially at a better understanding of the processes of star formation which take place in interstellar molecular clouds.

The fractal appearance of interstellar clouds

We shortly review the observational evidence for clumpy and fractal structure of interstellar clouds, and summarize work applying fractal descriptions to them. As an example, in the Taurus region the derived fractal dimensions (DH = 1.3−1.5) show no indications of smoother structures over four orders of magnitude in linear size down to the smallest resolution of 0.006 pc.

Revisiting the Narrative Approach of Estimating Tax Multipliers

A number of recent studies regress a “narratively” identified measure of a macroeconomic shock directly on an outcome variable. In this note, we argue that this approach can be viewed as the reduced-form regression of an instrumental variable approach in which the narrative time series is used as an instrument for an endogenous series of interest. We construct confidence bands for the case in which the narrative shock and the endogenous variable of interest are only weakly correlated. We apply the method to four narrative tax measures recently constructed by Romer and Romer (2010), Cloyne (2013), and Mertens and Ravn (2012). These variables turn out to be weak instruments for cyclically adjusted tax revenues. Compared to the single-equation estimation, we find that using any of the considered narrative tax measures as an instrument for cyclically adjusted tax revenues yields estimates of multipliers that are statistically indistinguishable from zero after correcting the confidence bands for weak instruments.

Tree-Based Conditional Portfolio Sorts: The Relation between Past and Future Stock Returns

Which variables provide independent information about the cross-section of future returns? Portfolio sorts and Fama-MacBeth regressions cannot easily answer this question when the number of candidate variables is large and when cross-terms might be important. We introduce a new method based on ideas from the machine learning literature that can be used in this context. Applying the method to past-return-based prediction of future returns, short-term returns become the most important predictors. A trading strategy based on our findings has an information ratio twice as high as a Fama-MacBeth regression accounting for two-way interactions. Transaction costs do not explain the results.

Selection Bias and the Cross-Section of Expected Returns

We propose an estimate of expected returns that accounts for selective anomaly submission and publication, and apply our adjustment to a broad cross-section of anomaly hedge portfolio returns. Selection bias accounts for a modest 10 to 15% of the typical in-sample return. This small selection bias is due to fact that the dispersion of in-sample returns is nearly twice as large as the typical standard error, indicating a significant amount of variation in true returns. Since the out-of-sample decline in returns is much larger than the selection effect, these results imply that investors learn about mispricing from academic research. Estimations on simulated data show that our bias adjustment is robust.

Did QE Lead to Lax Bank Lending Standards? Evidence from the Federal Reserve's LSAPs

Using confidential loan officer survey data on lending standards and internal risk ratings on loans, we document an effect of large-scale asset purchase programs (LSAPs) on lending standards and risk-taking. We exploit cross-sectional variation in banks’ holdings of mortgage-backed securities to show that the first and third round of quantitative easing (QE1 and QE3) significantly lowered lending standards and increased loan risk characteristics. The magnitude of the effects is about the same in QE1 and QE3, and is comparable to the effect of a one percentage point decrease in the Fed funds target rate.

Did QE Lead Banks to Relax Their Lending Standards? Evidence from the Federal Reserve's LSAPs

Using confidential loan officer survey data on lending standards and internal risk ratings on loans, we document an effect of large-scale asset purchase programs (LSAPs) on lending standards and risk-taking. We exploit cross-sectional variation in banks? holdings of mortgage-backed securities to show that the first and third round of quantitative easing (QE1 and QE3) significantly lowered lending standards and increased loan risk characteristics. The magnitude of the effects is about the same in QE1 and QE3, and is comparable to the effect of a one percentage point decrease in the Fed funds target rate.

Claim Dilution in the Municipal Debt Market

U.S state and local governments are increasingly turning to bank financing amid deteriorating fiscal positions. We document that the maturity and collateral structure of municipal bank loans allows borrowers additional debt capacity by diluting outstanding long-term bonds. Specifically, most municipal bank borrowers obtain loans with shorter maturities than long-term outstanding bonds, also providing municipalities with significant interest cost savings. Last, we show that municipalities substantially increase bank borrowing and decrease municipal bonds issuance in response to exogenous adverse income shocks. This suggests the upward trend in bank borrowing will likely persist if fiscal positions continue to decline.

Employment Effects of Unconventional Monetary Policy: Evidence from QE

This paper investigates the effect of the Federal Reserves unconventional monetary policy on employment via a bank lending channel. We find that banks with higher mortgage-backed securities holdings issued relatively more loans after the first and third rounds of quantitative easing (QE1 and QE3). While additional volume is concentrated in refinanced mortgages after QE1, increases are driven by newly originated home purchase mortgages and additional commercial and industrial lending after QE3. Using spatial variation, we show that regions with a high share of affected banks experienced stronger employment growth after both, QE1 and QE3. While the ability of households to refinance mortgages after QE1 spurred local demand, the resulting additional employment growth was relatively weak and confined to the non-tradable goods sector. In contrast, the increase in overall employment after QE3 is sizable and can be attributed to the supply of additional credit to firms. To s upport this finding, we use new confidential loan-level data to show that firms with stronger ties to affected banks increased employment and capital investment more after QE3. Altogether, our findings suggest that unconventional monetary policy can, similar to conventional monetary policy, affect real economic outcomes.