The Global Financial Crisis and the COVID-19 pandemic were two major shocks to the world economy in the 21st century. In this study, we analyze the patterns of recessions and recoveries of 101 advanced and developing economies. We identify the turning points of recessions and expansions between 1990 and 2022, and perform cross-country analysis of domestic and external drivers of economic recovery. In addition to the standard independent variables, we include institutional development, political stability, the extent of democracy, and trade restrictions indexes, and explore their roles in explaining recessions and recovery patterns. For the whole sample, we find that deeper recessions are followed by stronger recoveries, in line with Friedman’s plucking model of the business cycle. However, the empirical evidence for the plucking model becomes weaker if institutional development is limited and trade restrictions are high. We show that recessions that create conflict and trade tensions differ sharply from those that do not, a relevant finding in the current global climate of heightened trade tensions and geopolitical uncertainty. Finally, since developing countries tend to have weaker institutions and higher trade barriers, our evidence suggests that countercyclical monetary and fiscal policy will have to play a bigger role in cushioning global shocks in those countries. This, in turn, requires more robust and credible monetary and fiscal policy frameworks.

The problem of determining whether a given board of the puzzle Buttons & Scissors is solvable is known to be NP-complete. On the other hand, when the board is restricted to one dimension, it is known to be solvable in O(n3)-time for a board of size (length) n. This also holds when the button colors are limited to two colors. We provide a simple linear-time algorithm to determine whether an input of the Two-Color One-Dimensional Buttons & Scissors problem is solvable. The algorithm uses a necessary and sufficient condition after applying a linear-time preprocessing.

We re-examine the determinants of current account balances (CAB) and the saving-investment nexus with focus on emerging market and developing economies (EMDEs). We are in a new age in terms of facing not just economic challenges but also other non-economic challenges such as global climate changes, increasing natural disasters, and wars. We face the need to reexamine the determinants of CAB along with national saving and investment. We first take an event study approach, examining how these variables have evolved historically in the wake of wars, natural disasters, and pandemics. The second is a cross-country panel investigation of CAB, national saving, and of investment. In the presence of global financial instability, EMDEs tend to experience an improvement in CAB due to a fall in investment. A rise in oil prices increases both national saving and investment, but the change in investment is greater than the change in national saving, which worsens CAB. Contractionary monetary policy by the U.S. Federal Reserve Board tends to lower both national saving and investment, but the impact on CAB is not statistically different from zero. The more frequently a country experiences wars, on average, its CAB tends to improve. When a climatological or geographical disaster happens, all of its CAB, national saving, and investment tend to improve. A rise in the level of U.S. monetary policy uncertainty leads to an improvement in CAB, mainly due to a fall in investment.

We begin by examining determinants of aggregate foreign exchange reserve holdings by central banks (size of issuing country's economy and financial markets, ability of the currency to hold value, and inertia). But understanding the determination of reserve holdings probably requires going beyond the aggregate numbers, instead observing individual central bank behavior, including characteristics of the holding country (bilateral trade with the issuing country, bilateral currency peg, and proxies for bilateral exposure to sanctions), in addition to the characteristics of the reserve currency issuer. On a currency-by-currency basis, US dollar holdings are somewhat well explained by several issuer characteristics; but the other currencies are less successfully explained. It may be that the results from currency-by-currency estimation are impaired by insufficient sample size. This consideration offers a motivation for pooling the data across the major currencies and imposing the constraints that reserve holdings are determined in the same way for each currency. In this setting, most economic determinants enter with significance: economic size as measured by GDP, bilateral currency peg, and bilateral trade share. While one geopolitical factor (congruence in voting in the UN) is typically significant in the expected manner (with the exception of the US dollar), the other geopolitical factor (sanctions) does not enter with significance.

Abstract Introduction It has been recently reported there are big differences in pathophysiological and molecular phenotypes in mouse and human hypertrophic cardiomyopathy. These differences are observed all in terms of myocyte redox, mitochondrial number and respiration, mitochondrial reactive oxygen species generation and Ca2+ handling. Therefore we should search for molecules to be able to induce similar phenotype and molecular signaling both in mice and human. Mitochondrial ribosomal large subunit 44 (MRPL44) knockout mice were embryonic lethal, for which mutations are known to cause mitochondrial infantile cardiomyopathy and hypertrophic cardiomyopathy. Purpose Our purpose is to investigate the effect of MRPL44 haploinsufficiency in mice. Methods MRPL44 haploinsufficient (MRPL44+/-) mice were generated. Mineralocorticoid receptor-associated hypertension mice were induced in MRPL44+/- and wild-type (WT, MRPL44+/+) mice with subcutaneous infusion of aldosterone(Aldo) and 8% NaCl food for 4 weeks after uninephrectomy. Systolic blood pressure was measured by tail cuffs every week. WB, qPCR, cardiac echo, and histological examinations were performed. RNA sequencing analysis, electron microscopy examinations and mitochondrial activity assay were performed to find differences between MRPL44+/- and MRPL44+/+ mice. Results MRPL44 haploinsufficient mice spontaneously developed left ventricular hypertrophy in 6 weeks old. Heart rate, blood pressure, and cardiac systolic function were normal in MRPL44 haploinsufficient mice. MRPL44 was decreased about to 70% in MRPL44 haploinsufficient mice and mitochondrial arrangement were impaired in electron microscopic analysis. After Aldo treatment, blood pressure elevation were similar, however, MRPL44 haploinsufficient mice developed left ventricular systolic dysfunction and dilation compared with MRPL44+/+ mice. WB showed mitochondrial electron transport chain protein complex IV expression was significantly decreased. Furthermore, mitochondrial activity assay showed MRPL44 haploinsufficient mice had a significant reduction in complex IV activity, whereas complex I and II activity were similar to MRPL44+/+ mice. RNA sequencing analysis showed the significant changes in the expression of ribosomal subunits coded by nucleus in addition to mitochondrial ribosomal subunits. These results indicate MRPL44 plays an important role in the cardiac function of mitochondrial electron transport chain protein complexes via the expression of ribosomal protein subunits coded by both nucleus and mitochondria. Conclusions MRPL44 haploinsufficient mice spontaneously develop left ventricular hypertrophy and shows systolic dysfunction after aldosterone treatment accompanied with oxidative phosphorylation enzyme dysfunction.

Using a new set of trilemma indexes for exchange rate stability, financial market openness, and monetary policy independence, this paper first locates more than one hundred economies in the trilemma triangle over time. Second, the paper depicts individual economies’ trilemma regimes, defined by combinations of the three indexes, in the global map. Third, the paper tests econometrically the impact of monetary and fiscal policies on key macroeconomic variables (i.e., the real GDP growth rate gap, inflation, and their variability/volatility) under alternative trilemma regimes. Fourth, it examines the roles of trilemma regimes in influencing the macroeconomic variables. Econometric analysis uses a sample of 61 emerging market & developing economies over the period 1971–2020. The two-stage least squares estimation results largely support the Mundell-Fleming predictions made for three “corner” regimes. Monetary policy is effective in raising the real GDP growth rate gap and its variability under the “flexible exchange rate” corner regime, but not under the “financially open fixed rate” regime. Monetary policy is most effective in stimulating inflation and inflation volatility under the “flexible rate” regime. Fiscal policy has a positive impact on the GDP growth rate gap under the “flexible rate” regime and positive impacts on inflation and variability/volatility measures under the “financially closed fixed rate” regime, while it has no such impact under the “financially open fixed rate” regime, a somewhat surprising finding. The “financially open fixed rate” regime has a role of achieving price stability in a financially open economy.

A planar shape S is a k -fold tile if there is an indexed family T of planar shapes congruent to S that is a k -fold tiling: any point in R-2 that is not on the boundary of any shape in T is covered by exactly k shapes in T. Since a 1 -fold tile is clearly a k -fold tile for any positive integer k, the subjects of our research are nontrivial k -fold tiles, that is, plane shapes with property "not a 1 -fold tile, but a k(>= 2) -fold tile." In this paper, we prove some interesting properties about nontrivial k -fold tiles. First, we show that, for any integer k >= 2, there exists a polyomino with property "not an h -fold tile for any positive integer h < k, but a k -fold tile." We also find, for any integer k >= 2, polyominoes with the minimum number of cells among ones that are nontrivial k -fold tiles. Next, we prove that, for any integer k = 5 or k >= 7, there exists a convex unit -lattice polygon that is a nontrivial k -fold tile whose area is k, and for k = 2 and k = 3, no such convex unit -lattice polygon exists.

We assess market mediated financial integration over the last fifty years.We first systematically lay out several definitions of financial integration, and then review the evidence regarding whether covered interest parity, uncovered interest parity, and real interest parity hold across industrial and non-industrial countries.Finally we examine what the determinants of real interest differentials are.

Abstract Introduction Myosin phosphatase targeting subunit 2 (MYPT2) is a crucial subunit of cardiac myosin light chain (MLC) phosphatase. The phosphorylation of MLC in the ventricle plays a pivotal role in cardiac hypertrophy and function. Our previous study demonstrated that overexpression of MYPT2 activated MLC phosphatase leading to cardiac dysfunction. Mineralocorticoid receptor (MR)-related hypertension is associated with extensive cardiac fibrosis. It remains unknown whether MYPT2 may play a role in the development of cardiac fibrosis in MR-related hypertension. Purpose Our purpose is to investigate the effect of MYPT2 on cardiac fibrosis in MR-related hypertension. Methods After the knockdown of MYPT2 using MYPT2-siRNA, HL-1 cells (murine cardiomyocytes) were incubated with aldosterone (ALDO) for 24h. Cardiac-­specific MYPT2 knockout (c-MYPT2-/-) mice were generated using the Cre-lox system (αMHC-­Cre; MYPT2f/f). MR-related hypertension mice were induced in c-MYPT2-/- and wild-type (MYPT2+/+) mice with the subcutanouse infusion of ALDO and 8% NaCl food for 4 weeks after uninephrectomy. Systolic blood pressure (SBP) was measured by tail cuffs every week. WB, qPCR, cardiac echo, and histological examinations were performed. Results In HL-1 cells, ALDO increased the expression of connective tissue growth factor (CTGF), MYPT2, and the catalytic subunit of the type-1 phosphatase δ isoform (PP1cδ) in a concentration-dependent manner. MYPT2 protein levels significantly decreased by 80% in HL-1 cells transfected with MYPT2 siRNA compared with cells transfected with unspecific siRNA. Knockdown of MYPT2 significantly decreased the protein level of CTGF. In the mice model, the MYPT2 expression in the heart from MYPT2-/- mice was decreased to less than 30% compared with MYPT2+/+ mice. Heart rate, blood pressure, and cardiac systolic function were normal in c-MYPT2-/- mice. PP1cδ was decreased in c-MYPT2-/- mice compared with MYPT2+/+ mice. The expression of cardiac MLC kinase was not changed. The level of phosphorylation of MLC in c-MYPT2-/- mice was significantly higher than MYPT2+/+. Blood pressure elevation and left ventricular hypertrophy were observed in both MR-related hypertension mice. No significant difference in heart size and the nuclear localization of MR in cardiomyocytes. However, ejection fraction and fractional shortening in echocardiography were higher in c-MYPT2-/- than in MYPT2+/+ in MR-related hypertension mice. Histopathological examinations revealed the degree of fibrosis in c-MYPT2-/- mice was lower than in MYPT2+/+ mice with the decreased expression of CTGF. Conclusions Cardiac-specific deletion of MYPT2 resulted in a decrease of MLC phosphatase and an increase of phosphorylation in MLC in vivo. MYPT2 deletion can inhibit cardiac fibrosis in a MR-related hypertension model.

The challenges posed by big data in the 21st Century are complex: Under the previous common sense, we considered that polynomial-time algorithms are practical; however, when we handle big data, even a linear-time algorithm may be too slow. Thus, sublinear- and constant-time algorithms are required. The academic research project, “Foundations of Innovative Algorithms for Big Data,” which was started in 2014 and will finish in September 2021, aimed at developing various techniques and frameworks to design algorithms for big data. In this project, we introduce a “Sublinear Computation Paradigm.” Toward this purpose, we first provide a survey of constant-time algorithms, which are the most investigated framework of this area, and then present our recent results on sublinear progressive algorithms. A sublinear progressive algorithm first outputs a temporary approximate solution in constant time, and then suggests better solutions gradually in sublinear-time, finally finds the exact solution. We present Sublinear Progressive Algorithm Theory (SPA Theory, for short), which enables to make a sublinear progressive algorithm for any property if it has a constant-time algorithm and an exact algorithm (an exponential-time one is allowed) without losing any computation time in the big-O sense.

Over the years, policymakers have explored various combinations of varying degrees of monetary policy independence, exchange rate stability, and financial openness while recognizing that not all three policies can be achieved to the fullest extent – the “monetary trilemma” hypothesis. In recent years, holding international reserves (IR) has become an important policy instrument as a buffer or insurance against liquidity shortages. Significant and fundamental economic events such as currency crises have often changed the policy mix. In this paper, we find that countries’ policy mixes have been diverse and varied over time from the perspective of the trilemma and also IR holding. We then illustrate how the combination of the three trilemma policies and IR holding drastically changed before and after the Asian Financial Crisis (AFC). However, the Global Financial Crisis did not lead to a drastic change in the policy arrangements. We find that countries that faced large terms of trade shocks or negative economic growth during the crisis increase IR holding in the post-AFC. Countries that had negative growth during the crisis also tend to pursue more exchange rate flexibility and more open financial markets. This characteristic is true for commodity exporters, but not for manufacturing exporters. Countries with large current account deficit (i.e., “large capital borrowers”) tend to be more sensitive to economic growth at the time of the AFC. Countries that are under IMF stabilization programs or those with sovereign wealth funds tend to hold more IR. These characteristics were not found in the aftermath of the GFC. In general, countries increased their IR holdings after the GFC, but did not respond to the during-crisis economic and institutional conditions.

Facing acute strains in the offshore dollar funding markets during the COVID-19 crisis, the Federal Reserve (Fed) provided US dollar liquidity to the global economy by reactivating or enhancing swap arrangements with other central banks and establishing a new repo facility for financial institutions and monetary authorities (FIMA). This paper assesses motivations for the Fed liquidity lines, and the effects and spillovers of US dollar auctions by central banks using these lines. We find that the access to the Fed liquidity arrangements was driven by the recipient economies' close financial and trade ties with the US. Access to dollar liquidity also reflected global trade exposure. We find that announcements of expansion of Fed liquidity facilities or of auctions using these facilities led to appreciation of partner currencies against the US dollar and reduced these currencies' deviations from covered interest parity (CIP). Dollar auctions by major central banks (BoE, ECB, BoJ and SNB) had spillovers: they led to temporary appreciation of other currencies against the US dollar, reduced CIP deviations, and persistently reduced sovereign bond yields of other economies. However, dollar auctions done by non-major central banks with access to Fed facilities did not have a meaningful impact on key domestic financial variables. The impact of major central bank auctions does not differ by the economies' financial or trade links with the US or their balance sheet currency exposure, i.e. the major central bank auctions benefitted even the more vulnerable economies.

In a financially globalized world, managing long-term interest rates through short-term interest rates can be difficult. In this paper, we examine whether net capital inflows contribute to weakening the link between short- and long-term interest rates. We find that more financially open economies or those with more developed financial markets tend to have a greater negative relationship between net capital inflows and short- to long-term interest rate pass-through. We also examine whether macroprudential policies can affect the extent of interest rate pass-through and find that broad-based capital macroprudential tools are effective in retaining control of interest rate pass-through.

Planar/flat configurations of fixed-angle chains and trees are well studied in the context of polymer science, molecular biology, and puzzles. In this paper, we focus on a simple type of fixed-angle linkage: every edge has unit length (equilateral), and each joint has a fixed angle of $90^\circ$ (orthogonal) or $180^\circ$ (straight). When the linkage forms a path (open chain), it always has a planar configuration, namely the zig-zag which alternating the $90^\circ$ angles between left and right turns. But when the linkage forms a cycle (closed chain), or is forced to lie in a box of fixed size, we prove that the flattening problem -- deciding whether there is a planar noncrossing configuration -- is strongly NP-complete. Back to open chains, we turn to the Hydrophobic-Hydrophilic (HP) model of protein folding, where each vertex is labeled H or P, and the goal is to find a folding that maximizes the number of H-H adjacencies. In the well-studied HP model, the joint angles are not fixed. We introduce and analyze the fixed-angle HP model, which is motivated by real-world proteins. We prove strong NP-completeness of finding a planar noncrossing configuration of a fixed-angle orthogonal equilateral open chain with the most H--H adjacencies, even if the chain has only two H vertices. (Effectively, this lets us force the chain to be closed.)

Do central banks rebalance their currency shares?The answer matters because the dollar's predominant role in large official reserve holdings means that widespread rebalancing requires central banks to buy (sell) a depreciating (appreciating) dollar, stabilising its value against other major currencies.We hypothesise that larger reserve holdings have led central banks to approach their investment more systematically and to make rebalancing in the face of exchange rate changes the norm.We illustrate the choice with two polar case studies: the US clearly does not rebalance its small FX reserves; Switzerland does rebalance its very large reserves, so that changes in exchange rates do not move its currency allocation.Our hypothesis finds partial support in global aggregated data.They reject both no rebalancing and full rebalancing and point to emerging market economies as the source of the aggregate result.We also test for rebalancing with panel data and find that our sample economies on average again behave in intermediate fashion, partially but not fully rebalancing.However, when observations are weighted by the size of reserves, the panel analysis finds full rebalancing.A variety of control variables and splits of the panel sample do not alter the thrust of these findings.Central banks rebalance their FX reserves extensively but not uniformly.

Global current account imbalances have reappeared, although the extent and distribution of these imbalances are noticeably different from those experienced in the middle of the last decade. What does that recurrence mean for our understanding of the origin and nature of such imbalances? Will imbalances persist over time? Informed by empirical estimates of the determinants of current account imbalances encompassing the period after the global recession, we find that – as before – the observable manifestations of the factors driving the global saving glut have limited explanatory power for the time series variation in imbalances. Fiscal factors determine imbalances, and have accounted for a noticeable share of the recent variation in imbalances, including in the U.S. and Germany. For advanced economies, the financial component of the current account has been playing an increasing role in determining the movements of the account. Examining observable policy actions, it is clear that net official flows have been associated with some share of imbalances, although tracing out the motivations for intervention is difficult. Looking forward, it is clear that policy can influence global imbalances, although some component of the U.S. deficit will likely remain given the U.S. role in generating safe assets.

AbstractConstant-time algorithms are powerful tools, since they run by reading only a constant-sized part of each input. Property testing is the most popular research framework for constant-time algorithms. In property testing, an algorithm determines whether a given instance satisfies some predetermined property or is far from satisfying the property with high probability by reading a constant-sized part of the input. A property is said to be testable if there is a constant-time testing algorithm for the property. This chapter covers property testing on graphs and games. The fields of graph algorithms and property testing are two of the main streams of research on discrete algorithms and computational complexity. In the section on graphs in this chapter, we present some important results, particularly on the characterization of testable graph properties. At the end of the section, we show results that we published in 2020 on a complete characterization (necessary and sufficient condition) of testable monotone or hereditary properties in the bounded-degree digraphs. In the section on games, we present results that we published in 2019 showing that the generalized chess, Shogi (Japanese chess), and Xiangqi (Chinese chess) are all testable. We believe that this is the first results for testable EXPTIME-complete problems.