Three Essays on Labor Market Friction and the Business Cycle

This dissertation examines the macroeconomic impact of reduced labor market friction on the U.S. business cycle after the mid-1980s. The first two essays investigate the relationship between labor market flexibility and macroeconomic stability from a post-Keynesian perspective. In the third essay which reviews the relationship between labor market flexibility and patterns of U.S. business cycle, I test the argument that after 1985 Okun’s coefficient became larger due to the flexible labor market. In essay 1, considering two aspects of labor market flexibility, employment flexibility and real wage flexibility, I adopt the flex-output model (Skott, 2015) to first discuss employment flexibility and then extend it by incorporating real wage dynamics induced from a wage-price Phillips curve (Flaschel and Krolzig, 2006) to address real wage flexibility. The simulation of model explains that employment flexibility increases instability of an economy whereas real wage flexibility reduces it. Empirical results of this paper suggest that during the Great Moderation, real wage flexibility played a major role in stabilizing the U.S. economy. On the other hand, employment flexibility has contributed to destabilizing the economy during the Great Recession. In essay 2, using structural VAR analysis, I provide more rigorous empirical evidence to support the hypothesis in essay 1—real wage flexibility played a major role in stabilizing U.S. economy during the Great Moderation, and employment flexibility has contributed to destabilizing the economy during the Great Recession. I found that during the Great Moderation (1) Employment and real wage flexibilities were operating simultaneously; (2) The employment flexibility was not so severe; (3) Flexible real wages functioned as an autonomic stabilizer; (4) Therefore, stabilized goods market during the Great Moderation can be explained by dominating effect of the real wage flexibility over the employment flexibility. For the Great Recession, however, severe asymmetry in the business cycle and the lack of observations obstructs reliable empirical work. In essay 3, I discuss the observations of increased cyclicality in aggregate hours and increased responsiveness of the (un)employment rate to output changes after 1985, which have contributed to recent debate about the validity of Okun’s law. To investigate this, I measure Okun’s coefficients in three phases of the business cycle—recessions, early expansions and late expansions. Related findings include: (1) The main determining factor for an increased coefficient for aggregate hours is the increased responsiveness of the employment rate during late expansions. (2) The increased responsiveness of hours per employee in early expansion is another main determining factor for more reactive aggregate hours. These findings conflict with the flexible labor market hypothesis that focuses mainly on firms’ firing behaviors during recessions when they incur less costs than previously

Class Struggle and Economic Flactuations: VAR Analysis of the post-War U.S. Economy

Building on Marx’s insights in Chapter 25, Volume I of Capital, an augmented version of the cyclical profit squeeze (CPS) theory offers a plausible explanation of macroeconomic fluctuations under capitalism. The pattern of dynamic interactions that emerges from a 3-variable (profit share, unemployment rate and nonresidential fixed investment) vector autoregression estimated with quarterly data for the postwar U.S. economy is consistent with the CPS theory for the regulated (1949Q1–1975Q1) as well as for the neoliberal periods (starting in 1980 or in 1985). Hence, the CPS mechanism seems to be in operation even under neoliberalism. JEL Categories: B51; C22cyclical profit squeeze, vector autoregression

Ride Quality Control of a Full Vehicle Suspension System Featuring Magnetorheological Dampers With Multiple Orifice Holes

This study proposes a relationship between the ride comfort of passenger vehicles and two different types of magnetorheological (MR) dampers, with and without orifice holes in the piston. To achieve superior ride comfort, two cylindrical-type MR dampers with identical dimensions (piston radius, pole lengths, and the distance between two poles) are proposed. One of the MR dampers adds the orifice holes in the piston bobbin to obtain a relatively low damping force slope in the low piston velocity region. To enhance the ride quality of a passenger vehicle, the damping force slope of the rear damper should be more gradual than that of the front damper. Thus, it can be inferred that identical semi-active vehicle systems require normal MR dampers in the front and MR dampers with orifice holes in the rear, with proper control strategies. To evaluate ride performance, a robust sliding mode controller was designed. It is demonstrated through simulation that the proposed vehicle system produces better ride comfort than vehicle systems equipped with only one type of MR damper

Surgical castration efficiently delays the time of starting a systemic chemotherapy in castration-resistant prostate cancer patients refractory to initial androgen-deprivation therapy

AbstractBackgroundThe aim of this study was to investigate the effects of surgical castration, particularly delaying the time to entrance of systemic chemotherapy, in castration-resistant prostate cancer (CRPC) patients who were refractory to initial combination androgen deprivation therapy.Materials and methodsWe analyzed the clinical data of 14 CRPC patients diagnosed at Seoul National University Bundang Hospital (SNUBH) from November 2008 through May 2015. After exclusion of three patients, we finally analyzed the baseline characteristics of 11 CRPC patients. We also assessed the delaying time of docetaxel administration, which was defined as response duration, after surgical castration.ResultsAfter bilateral orchiectomy, the treatment response rate was 45.4% and the median duration of response was 9 months (range 4–48 mo). Responders had less aggressive biopsy Gleason scores compared to nonresponders. Notably, responders showed the reducing pattern of serum prostate specific antigen levels, while nonresponders demonstrated increasing tendency after surgical castration. Moreover, responders also presented with a reduction pattern of serum testosterone levels, whereas nonresponders showed an increasing pattern of testosterone levels after bilateral orchiectomy.ConclusionsIn summary, despite the limited number of cases for convincing evidence, our results shed light again on the clinical benefits of surgical castration prior to the systemic chemotherapy in some CRPC patients after initial hormone therapy

Tracing the historical origin of Joseon mummies considering the structural similarities between the burial systems of Korean and Chinese dynasties

Joseon mummies have proved to be excellent subjects for scientific research on the health and disease statuses of pre-modern Korean peoples. Despite its academic significance, the origins of the Hoegwakmyo tomb in which the Joseon mummy was discovered have not yet been entirely revealed. Meanwhile, over the past several decades, there have been some reports on mummies and cultural artifacts preserved very well in the tombs of several Chinese dynasties (especially Song, Yuan, Ming and Qing). Although the Chinese tombs were very diverse in structure, we note that some graves among them were structurally very similar to Joseon Hoegwakmyo tombs. Before the Hoegwakmyo tomb in Korea, there were already similar tombs in China, inside which dead persons were mummified like the Joseon mummies. Considering that the Hoegwakmyo tomb of the Joseon Dynasty was established by the influence of the Confucian ideology, the Korean and Chinese mummies might share common cultural origins in history

Retinoic acid modulation of granule cell activity and spatial discrimination in the adult hippocampus

Retinoic acid (RA), derived from vitamin A (retinol), plays a crucial role in modulating neuroplasticity within the adult brain. Perturbations in RA signaling have been associated with memory impairments, underscoring the necessity to elucidate RA’s influence on neuronal activity, particularly within the hippocampus. In this study, we investigated the cell type and sub-regional distribution of RA-responsive granule cells (GCs) in the mouse hippocampus and delineated their properties. We discovered that RA-responsive GCs tend to exhibit a muted response to environmental novelty, typically remaining inactive. Interestingly, chronic dietary depletion of RA leads to an abnormal increase in GC activation evoked by a novel environment, an effect that is replicated by the localized application of an RA receptor beta (RARβ) antagonist. Furthermore, our study shows that prolonged RA deficiency impairs spatial discrimination—a cognitive function reliant on the hippocampus—with such impairments being reversible with RA replenishment. In summary, our findings significantly contribute to a better understanding of RA’s role in regulating adult hippocampal neuroplasticity and cognitive functions

Changes in Oral Vowel Sounds and Hyoid Bone Movement After Thyroidectomy

Objectives Voice and speech alterations after total thyroidectomy may be associated with other extralaryngeal factors, such as neck muscle dysfunction and neck scar contracture. We evaluated the acoustic characteristics of oral vowel sounds and changes in hyoid bone movement before and after thyroidectomy. Methods Twenty-nine female patients undergoing total thyroidectomy were included. Fundamental frequencies (Fo), formants and vowel space areas were evaluated before surgery and 7 days and 3 months after surgery to acoustically analyze the oral vowel sounds. Videofluoroscopic images were taken at the same times to evaluate hyoid bone movement. Results The Fo levels of seven vowels decreased significantly after surgery. The vowel formant changes the F1 of vowel /[e]/ decreased significantly from baseline at 3 months postoperatively, and the F3 of vowel /[i]/ decreased significantly from baseline 7 days postoperatively. The change in the vowel space area was not observed. The Y coordinate of the vowels /[i]/ and /[e]/ decreased significantly from baseline 7 days postoperatively due to changes in hyoid movement. Conclusion The damage to the neck muscles after thyroidectomy changes in Fo, formant and hyoid bone position. These quantitative results could be used as basic data for voice management in patients who undergo thyroidectomy