Entrepreneurship and the extensive margin in export growth : a microeconomic accounting of Costa Rica's export growth during 1997-2007

The literature on the correlation between exports and economic development runs deep into the history of economic thought and permeates policy debates. This paper studies the microeconomic structure of export growth in Costa Rica, with special emphasis on the extensive margin of trade, encompassing new exporting firms, new products, and new export markets, as well as the unit values of new versus incumbent products. The data suggest that few new firms survive the test of exporting -- more than 40 percent of firms exit export activities after one year -- and this firm turnover is associated with a steady deterioration of export unit values (prices). Furthermore, most new export products are associated with product switching by incumbent exporting firms. The typical new product introduced by incumbent firms tended to be priced at about 90 percent of the unit values of incumbent products. In contrast, the usual suspected obstacles to export growth, such as the inability of small firms to enter exporting activities or to grow their exports, appear to be important sources of export growth. In fact, the smallest exporting firms experienced the fastest growth in their export values. Some of these results are compared with those from other countries that have been examined in related literature.Economic Theory&Research,Markets and Market Access,Airports and Air Services,Microfinance,Tax Law

Golden Probe of the Top Yukuwa

We perform a preliminary study of the ability of the Higgs decay to four leptons to shed light on the top quark Yukawa couplings. In particular we examine whether the $h\to 4\ell$ `golden channel' is sensitive to the $CP$ properties of the top quark couplings to the Higgs boson. We show that kinematic distributions are sensitive to interference of the next-to-leading order electroweak corrections with the tree level $ZZ$ contribution. This translates into a sensitivity to the top quark Yukawa couplings such that meaningful constraints on their $CP$ properties can begin to be obtained once $\sim 300$ fb$^{-1}$ of data has been collected at $\sim 14$ TeV, with significant improvements at higher luminosity or with a higher energy hadron collider. This makes the $h\to4\ell$ channel a useful probe of the top quark Yukawa couplings that is qualitatively different from already established searches in $h\to V\gamma$ two body decays, $tth$, and $gg\to h$. We also briefly discuss other potential possibilities for probing the top Yukawa $CP$ properties in $h\to2\ell\gamma$ and $\ell^+\ell^-\to h Z, h\gamma$.Comment: references and footnote adde

Golden Probe of Electroweak Symmetry Breaking

The ratio of the Higgs couplings to $WW$ and $ZZ$ pairs, $\lambda_{WZ}$, is a fundamental parameter in electroweak symmetry breaking as well as a measure of the (approximate) custodial symmetry possessed by the gauge boson mass matrix. We show that Higgs decays to four leptons are sensitive, via tree level/1-loop interference effects, to both the magnitude and, in particular, overall sign of $\lambda_{WZ}$. Determining this sign requires interference effects, as it is nearly impossible to measure with rate information. Furthermore, simply determining the sign effectively establishes the custodial representation of the Higgs boson. We find that $h\to4\ell$ ($4\ell \equiv 2e2\mu, 4e, 4\mu$) decays have excellent prospects of directly establishing the overall sign at a high luminosity 13 TeV LHC. We also examine the ultimate LHC sensitivity in $h\to4\ell$ to the magnitude of $\lambda_{WZ}$. Our results are independent of other measurements of the Higgs boson couplings and, in particular, largely free of assumptions about the top quark Yukawa couplings which also enter at 1-loop. This makes $h\to4\ell$ a unique and independent probe of the electroweak symmetry breaking mechanism and custodial symmetry.Comment: 8 page