Labor Supply of New York City Cabdrivers: One Day at a Time

Life-cycle models of labor supply predict a positive relationship between hours supplied and transitory changes in wages. We tested this prediction using three samples of wages and hours of New York City cabdrivers, whose wages are correlated within days but uncorrelated between days. Estimated wage elasticities are significantly negative in two out of three samples. Elasticities of inexperienced drivers average approximately −1 and are less than zero in all three samples (and significantly less than for experienced drivers in two of three samples). Our interpretation of these findings is that cabdrivers (at least inexperienced ones): (i) make labor supply decisions “one day at a time” instead of intertemporally substituting labor and leisure across multiple days, and (ii) set a loose daily income target and quit working once they reach that target

A Thing of Beauty: Steering Behavior in an Interactive Playground

Interactive playgrounds are spaces where players engage in collocated, playful activities, in which added digital technology can be designed to promote cognitive, social, and motor skills development. To promote such development, different strategies can be used to implement game mechanics that change player's in-game behavior. One of such strategies is enticing players to take action through incentives akin to game achievements. We explored if this strategy could be used to influence players' proxemic behavior in the Interactive Tag Playground, an installation that enhances the traditional game of tag. We placed the ITP in an art gallery, observed hundreds of play sessions, and refined the mechanics, which consisted in projecting collectible particles around the tagger that upon collection by runners resulted only in the embellishment of their circles. We implemented the refined mechanics in a study with 48 children. The playground automatically collected the players' positions, and analyses show that runners got closer to and moved more towards taggers when using our enticing strategy. This suggests an enticing strategy can be used to influence physical in-game behavior

Manipulation of Plant Defense Responses by the Tomato Psyllid (Bactericerca cockerelli) and Its Associated Endosymbiont Candidatus Liberibacter Psyllaurous

Some plant pathogens form obligate relationships with their insect vector and are vertically transmitted via eggs analogous to insect endosymbionts. Whether insect endosymbionts manipulate plant defenses to benefit their insect host remains unclear. The tomato psyllid, Bactericerca cockerelli (Sulc), vectors the endosymbiont “Candidatus Liberibacter psyllaurous” (Lps) during feeding on tomato (Solanum lycopersicum L.). Lps titer in psyllids varied relative to the psyllid developmental stage with younger psyllids harboring smaller Lps populations compared to older psyllids. In the present study, feeding by different life stages of B. cockerelli infected with Lps, resulted in distinct tomato transcript profiles. Feeding by young psyllid nymphs, with lower Lps levels, induced tomato genes regulated by jasmonic acid (JA) and salicylic acid (SA) (Allene oxide synthase, Proteinase inhibitor 2, Phenylalanine ammonia-lyase 5, Pathogenesis-related protein 1) compared to feeding by older nymphs and adults, where higher Lps titers were found. In addition, inoculation of Lps without insect hosts suppressed accumulation of these defense transcripts. Collectively, these data suggest that the endosymbiont-like pathogen Lps manipulates plant signaling and defensive responses to benefit themselves and the success of their obligate insect vector on their host plant

Tomato Pathogenesis-related Protein Genes are Expressed in Response to Trialeurodes vaporariorum and Bemisia tabaci Biotype B Feeding

The temporal and spatial expression of tomato wound- and defense-response genes to Bemisia tabaci biotype B (the silverleaf whitefly) and Trialeurodes vaporariorum (the greenhouse whitefly) feeding were characterized. Both species of whiteflies evoked similar changes in tomato gene expression. The levels of RNAs for the methyl jasmonic acid (MeJA)- or ethylene-regulated genes that encode the basic β-1,3-glucanase (GluB), basic chitinase (Chi9), and Pathogenesis-related protein-1 (PR-1) were monitored. GluB and Chi9 RNAs were abundant in infested leaves from the time nymphs initiated feeding (day 5). In addition, GluB RNAs accumulated in apical non-infested leaves. PR-1 RNAs also accumulated after whitefly feeding. In contrast, the ethylene- and salicylic acid (SA)-regulated Chi3 and PR-4 genes had RNAs that accumulated at low levels and GluAC RNAs that were undetectable in whitefly-infested tomato leaves. The changes in Phenylalanine ammonia lyase5 (PAL5) were variable; in some, but not all infestations, PAL5 RNAs increased in response to whitefly feeding. PAL5 RNA levels increased in response to MeJA, ethylene, and abscisic acid, and declined in response to SA. Transcripts from the wound-response genes, leucine aminopeptidase (LapA1) and proteinase inhibitor 2 (pin2), were not detected following whitefly feeding. Furthermore, whitefly infestation of transgenic LapA1:GUS tomato plants showed that whitefly feeding did not activate the LapA1 promoter, although crushing of the leaf lamina increased GUS activity up to 40 fold. These studies indicate that tomato plants perceive B. tabaci and T. vaporariorum in a manner similar to baterical pathogens and distinct from tissue-damaging insects

Sức mạnh của sự tử tế : Cách chinh phục giới kinh doanh bằng sự tử tế

177 tr. ; 21 cm

Caveat Compounder: A Warning about Using the Daily CRSP Equal-Weighted Index to Compute Long-Run Excess Returns

This paper issues a warning that compounding daily returns of the Center for Research in Security Prices (CRSP) equal-weighted index can lead to surprisingly large biases. The differences between the monthly returns compounded from the daily tapes and the monthly CRSP equal-weighted indices is almost 0.43 percent per month, or 6 percent per year. This difference amounts to one-third of the average monthly return, and is large enough to reverse the conclusions of a paper using the daily tape to compute the return on the benchmark portfolio. We also investigate the sources of these biases and suggest several alternative strategies to avoid them