In this paper, in addition to some elementary facts about the ultra-groups, which their structure based on the properties of the transversal of a subgroup of a group, we focus on the relation between a group and an ultra-group. It is verified that every group is an ultra-group, but the converse is not true generally. We present the conditions under which, for every normal subultra-group of an u...

Trade costs have fallen surprisingly little given the large increase in international trade in the last 50 years. This paper examines whether trade costs are properly measured. I show theoretically that trade weighted measures will underestimate the changes in trade costs when there are fixed market entry costs and quality differences. Newly traded goods enter at higher trade costs than previou...

The evidence reveals that young children are targeted by food and beverage advertisers but are unable to comprehend the commercial context and persuasive intent of marketing. Although the First Amendment protects commercial speech, it does not protect deceptive and misleading speech for profit. Marketing directed at children may fall into this category of unprotected speech. Further, children d...

One of the most striking development in the world trading system since the mid 1990s is a surge in Regional Trade Agreements (RTAs). From about 50 till 1990, the number of RTAs notified to the World Trade Organization (WTO) has crossed 250 in 2003 and estimates indicate that over 300 RTAs will be in effect by 2007. Initially WTO encouraged the growth of RTAs because it believed that regional in...

In this paper, we aim at investigating from a game theory perspective whether trade liberalization can promote a collusive intra-industry trade and whether such a collusive trade is always socially desirable compared to the autarchy solution. We show that, under Cournot competition, economic integration is anti-competitive if collusive trade is a possible outcome of the repeated game; under pri...

this paper is analysing the role of economic reforms on the labour market in iranian industry in economic reform period (1990-2005), and in turn, it is comparing it with closed economic period (1979-1989). in order to do the above comparative analysis, the manufacturing industry has been categorized based on hecksher-ohlin and gause methodology. accordingly, we have some industrial groups, incl...

The main objective of this study is to evaluate the impact of maritime transportation instability on international trade instability based on wavelet smoothing and spatial panel data econometric method during the period 1990-2012. The results showed that the spatial effects have an impact on international trade instability. So that a sudden 100 percent increase in international trade in the nei...

Social insects provide good model systems for testing trade-offs in decision-making because of their marked reproductive skew and the dilemma workers face when to reproduce. Attaining reproductive skew requires energy investment in aggression or fertility signaling, creating a trade-off between reproduction and dominance. This may be density-dependent because the cost of achieving dominance may...