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We measured physical properties and optical properties of the black carbon (BC) generated in a spark discharger which did not produce soluble organic fractions. Effective densities and absorption cross-sections of the fresh BC were estimated using the electrical mobility diameter, the number concentration and the mass concentration. Size distribution measurements using a differential mobility analyzer (DMA) and a condensation particle counter (CPC) showed that the mode diameter and the number concentration increased with increasing spark frequency of the spark discharger. The primary particle size was also measured through the analysis of images observed using a field emission scanning electron microscope (FESEM), decreasing from 36.3 to 15.1 nm with increasing a spark frequency. The effective densities were estimated from 0.054 to 1.392 g/cm 3 and compared to be lower than those of atmospheric aerosols which might be aged. The absorption cross-sections were estimated as 1.0×10 –15 to 1.7×10 –15 m 2 depending on spark frequency. For the BC generated at a fixed constant spark frequency, the absorption cross-section was estimated to be larger as the BC became bigger in electrical mobility diameter. For the BC having the same electrical mobility diameter generated at different spark frequencies, however, the absorption cross-section generated at a faster spark frequency was smaller. Fractal dimension for the BC larger than 160 nm was measured to be 1.79, which is very similar to that for the spark-generated BC studied by other research group. In conclusion, the effective density allowed us to distinguish the core BC from aged BC.

I present a model in which (1) a more talent-demanding task increases both rewards for high talent and the penalty for low talent due to a greater fixed cost of production, and (2) individual talent is task-specific and talent updates occur only for tasks near the attempted task, which implies a task-sequence problem in which the initial task constrains subsequent task choices. Rising talent rewards and penalty stemming from a rising scale economy motivate young workers to choose a more talent-demanding task, raise the failure rate (i.e., the probability of the updated talent being lower than the exit threshold), and concentrate income gains in a diminishing fraction of high-talent workers. Rising talent rewards and penalty also increase the share of young workers subject to binding minimum current-income constraints, thus increasing the dispersion of tasks among young workers. The model sheds light on the rising stratification of careers among young workers and the rising polarization of the residual labor income distribution (i.e., the labor income distribution controlling for observable worker characteristics such as education and age).

Black carbon(BC) aerosols were monitored at the KIST site(37.603°N, 127.046°E) and Cheonan-KOREATECH site(36.766°N, 127.281°E) during the pre KORea-US Air Quality Study(KORUS-AQ) campaign using a couple of Muliti Angle Absorption Photometers(MAAP). BC mass concentrations were presented as 2.14μg/m± 3 1.06 and 0.94±0.60 μg/m 3 at KIST site(Seoul) and KOREATECH site(Cheonan), respectively. BC mass concentrations measured at KIST and KOREATECH sites from 22:00 on May 22 to 12:00 on May 23, 2015 showed 80% and 72% higher than average BC mass concentrations measured during campaign period, respectively. It indicates both sites could be influenced by a remote source. Similar patterns of BC concentrations between two sites from 20:00 to 24:00 on June 6, 2015 implies that the BC could be transported into both sites and then be stagnant inside the Korean Peninsula. Diurnal variation of BC in weekdays and weekends were also presented for the KIST and KOREATECH sites. Morning rush hour peak was observed at KIST site located in metropolitan area though no distinct morning rush hour peak was not observed at KOREATECH site located in a suburban area. This study revealed transport pathways of BC near the Korean Peninsula using back-trajectory analysis of BC measured both in a metropolitan area and in a suburban area.

I explore the effects of economic and political integration on economic growth in a model of vintage human capital and sequential intergenerational bargains. Adoption of a new technology raises not only the productivity but also the bargaining position of the future generations, creating a bias for the current generations to preserve the current technology. Economic integration (i.e., the sharing of frontier technology among countries) promotes growth if there is a diversity in human capital distribution or a coordination failure across countries. On the other hand, political integration (i.e., the merging of countries into a single bargain) promotes stagnation as it eliminates the diversity and coordination failures.

We show that business education/occupations have expanded and that technical education/occupations have contracted in the Czech Republic and Poland since 1990. We interpret these changes as an adjustment necessary for their transition to a market economy. We do not find the same pattern in Hungary, which we attribute to the earlier timing of its transition. We construct an aggregate model in which labour reallocates in response to changing demand structure. When calibrated with the Czech and Polish data, the model generates a large movement of workers with technical education and experience into business occupations in the early 1990s. The discounted sum of output loss due to the gap between the demand structure and the composition of existing human capital amounts to between 8 and 40 percent of 1990 GDP.

The authors examine the role of organized labor in the restructuring experience of two coal-mining regions in the Czech Republic and Romania in the 1990s. Under similar external circumstances, the Ostrava region of the Czech Republic undertook early gradual restructuring, whereas the Jiu Valley region in Romania did not undertake restructuring until 1997, which was followed by massive layoffs in the sector. The authors conduct a quantitative exercise that accounts for mine productivity, labor-market conditions, and constraints in compensating laid-off miners. They show that the belated restructuring in the Jiu Valley was inefficient: gradual restructuring with reasoned compensation would have benefited both the miners and the state. An important factor in the delayed restructuring was the miners’ resistance to it. The authors discuss what motivated the miners’ opposition and the consequences.

Mobility restrictions (e.g., severance payment, life-long tenure, and divorce ban) are widely observed. I present a partnership model that highlights the 'break-up externality' (i.e., the negative effect of a person's break-up decision on his current partner). Under this externality, there is too much searching for new partners and too much breaking-up of existing partnerships. Restrictions such as a break-up payment and break-up ban can reduce the levels of searching and breaking-up and improve welfare. Thus the paper rationalizes mobility restrictions as welfare-improving arrangements. (Copyright: Elsevier)

I propose the aggregate output divided by the wage rate of an industrial laborer in a country as a measure of the aggregate human capital input for that country. I use this method to compare the human capital inputs for 45 countries of diverse output levels. I find that human capital input differs between the lowest-income and the highest-income countries by a factor of 2.2 or 2.8, depending on the inclusion of outlier countries. This is significant but small relative to the results from the method based on years of schooling.

I present a model in which randomly matched pairs of people bargain over the division of output in each period. Output can be consumed or stored for later consumption. People are identical except possibly in wealth (i.e., the stored output). The one-period utility is linear except for the starvation disutility (i.e., the additional drop in utility under no consumption). The starvation disutility weakens the bargaining position of a poor person and strengthens that of a rich person in an otherwise symmetric bargaining, providing the incentive to accumulate wealth. Policies that deincentivize wealth accumulation (e.g., wealth tax, progressive income tax) can make both the rich and the poor become better off. matters.

We examine the role of organized labour in the restructuring experience of two coal-mining regions in the 1990s. Under similar external circumstances, the Czech Republic’s Ostrava region underwent gradual restructuring from early on whereas Romania’s Jiu Valley region went through no restructuring until 1997 followed by massive layoffs over 2 years. We conduct a quantitative exercise that accounts for mine productivity, labour market conditions and the constraints in compensating laid-off miners. We show that the Jiu Valley’s delay in restructuring was inefficient. Gradual restructuring with compensation would have benefited both the miners and the government. The proximate reason for the delay was the Jiu Valley miners’ action against restructuring. We discuss what motivated their action and why it was effective.

I study the choice of technology adoption in an environment where human capital is transmitted from the old to the young generation, but the young generation can opt out for a new technology. The adoption and matching decisions are made in a sequential intergenerational bargaining. Since technology adoption benefits future generations who do not participate in the bargaining, there is an inherent bias toward preserving the current technology. The main result is that economic integration (i.e., the sharing of frontier technology among countries) promotes growth while political integration (i.e., the merging of countries into a single bargaining) promotes stagnation.

I present a model of a proprietary regime with opportunities for direct production (e.g., plantation cultivation, mining extraction). The premise is that direct production is a superior method of appropriation than taxation. The tax and spending policy of the regime distorts the resource allocation in favor of direct production and at a loss of private production; the welfare of the population suffers while the regime benefits. I examine the relevance of the model to the policies of actual proprietary regimes.

I present a model in which the employment contract includes severance payment as an instrument for achieving optimal separation between the firm and the worker. I show that the privately optimal severance payment from the model can replicate the level and the variation in actual severance payments (and notice periods) across OECD countries. I conduct a policy experiment in which the existing unemployment benefits are financed by a separation tax. Under this policy, the actual severance payments need to change only marginally in order to achieve socially optimal separation.

I propose the aggregate output divided by the wage rate of the industrial labourer in a country as a measure of the aggregate human capital input for that country. The justification is that the skills and the health of industrial labourers are comparable across countries; therefore their human capital input can serve as a unit in the measurement. For international comparison, this method is better than other methods based on schooling, conceptually or in terms of applicability, given the data constraints for low-income countries. I use this method to compare the human capital inputs for 39 countries of diverse output levels. I find that human capital input differs between the lowest-income and the highest-income countries by a factor of about 2. This is significant but small relative to their output difference or the results from other methods. In neoclassical output accounting, the human capital input differences across countries, even after being combined with their physical capital input differences, leave a large pat of their output differences unaccounted for.

Bad policies (i.e., policies harmful to private producers such as excessive taxation, arbitrary confiscation, and negligence of pubic goods) are observed in quite a few countries. These countries tend to have autocratic regimes.I explore a reason why bad policies may benefit autocrats.I present a model economy where the autocrat manages his production (e.g., military exploits, plantation cultivation, mining) in addition to setting policies for the private producers. The autocrat has an incentive to repress the income level of private producers: it reduces the wage rate that he must offer to his workers and thereby increases the surplus from his production. Thus the autocrat chooses a tax rate that is higher than the revenue-maximizing rate: it lies on the backward-bending part of the Laffer curve. He may also choose to lower the productivity of private producers through confiscation, neglect of public goods, and other non-tax policies. I argue that the story is helpful in understanding bad policies present in militaristic regimes of the Ottoman and Mughal empires, Trujillo's regime in the plantation- based economy of the Dominican Republic, and Mobutu's regime in mineral- rich Zaire.

Mobility restrictions (e.g., severance payment, life-long tenure, and divorce ban) are widely observed. This paper is an attempt to understand why there are these restrictions. I present a model economy that features production teams and focuses on the search for partners and the formation and break-up of teams. Under no restrictions, there is too much searching and breaking-up because the individual decision problem ignores the loss of the deserted partner’s utility. Arrangements such as break-up payment and break-up ban can improve welfare. Thus the paper rationalizes mobility restrictions as welfare-improving arrangements.

I explore how and and to what extent policy uncertainty can account for the observed long-run cross-country differences in capital price and levels of aggregate investment and output. I present a model economy where the industry-level policy-related investment cost is uncertain. Holding the average one-period investment cost constant, policy uncertainty leads to a higher capital price and subsequently to lower levels of long-run aggregate investment and output. Policy uncertainty also makes industry-level investment more volatile. In an investigation of industry-level investment across countries, I find that, consistent with the model, industry-level investment in lower-income countries is more volatile. I calibrate the model so that the simulated investment sequences from the model mimic the actual investment sequences. I find that policy uncertainty can account for large differences in long-run capital price, investment, and output across countries. Between the lowest-income and the highest-income countries, policy uncertainty can account for the capital price difference by a factor of about three, and can account for investment and output level differences of a similar magnitude.