These slides were developed for an invited public lecture at Indiana University--Bloomington, delivered in November 2009. Note 1: Downloadable .pdf includes embedded video files that play automatically if supported by your reader. Note 2: The two research articles (see slide 2) on which this lecture is based are available for download here: http://www.business.otago.ac.nz/econ/Personal/ts_files/mcd.pdf and here: http://www.business.otago.ac.nz/econ/Personal/ts_files/natural.pdf