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D.B. Dunson 285els in spatial statistics, computer experiments and beyond. These algorithms,combined with increasing knowledge of theoretical properties and characterizations,stimulated an explosion of modeling innovation starting in the early2000s but really gaining steam by 2005. A key catalyst in this exponentialgrowth of research activity and innovation in NP Bayes was the dependentDirichlet process (DDP) of Steve MacEachern, which ironically was neverpublished and is only available as a technical report. The DDP and other keymodeling innovations were made possible by earlier theoretical work providingcharacterizations, such as stick-breaking (Sethuraman, 1994; Ishwaran andJames, 2001) and the Polya urn scheme/Chinese restaurant process (Blackwelland MacQueen, 1973). Some of the circa 2005–10 innovations include theIndian buffet process (IBP) (Griffiths and Ghahramani, 2011), the hierarchicalDirichlet process (HDP) (Teh et al., 2006), the nested Dirichlet process(Rodríguez et al., 2008), and the kernel stick-breaking process (Dunson andPark, 2008).One of the most exciting aspects of these new modeling innovations wasthe potential for major applied impact. I was fortunate to start working onNP Bayes just as this exponential growth started to take off. In the NP Bayesstatistics community, this era of applied-driven modeling innovation peakedat the 2007 NP Bayes workshop at the Issac Newton Institute at CambridgeUniversity. The Newton Institute is an outstanding facility and there was anenergy and excited vibe permeating the workshop, with a wide variety of topicsbeing covered, ranging from innovative modeling driven by biostatisticalapplications to theoretical advances on properties. One of the most excitingaspects of statistical research is the ability to fully engage in a significantapplied problem, developing methods that really make a practical differencein inferences or predictions in the motivating application, as well as in otherrelated applications. To me, it is ideal to start with an applied motivation,such as an important aspect of the data that is not captured by existing statisticalapproaches, and then attempt to build new models and computationalalgorithms that have theoretical support and make a positive difference to thebottom-line answers in the analysis. The flexibility of NP Bayes models makesthis toolbox ideal for attacking challenging applied problems.Although the expansion of the NP Bayes community and impact of theresearch has continued since the 2007 Newton workshop, the trajectory andflavor of the work has shifted substantially in recent years. This shift is duein part to the emergence of big data and to some important cultural hurdles,which have slowed the expansion of NP Bayes in statistics and scientificapplications, while stimulating increasing growth in machine learning. Culturally,statisticians tend to be highly conservative, having a healthy skepticismof new approaches even if they seemingly improve practical performance inprediction and simulation studies. Many statisticians will not really trust anapproach that lacks asymptotic justification, and there is a strong preferencefor simple methods that can be studied and understood more easily. This is