A three-dimensional chemical transport model (CTM) is used to study the stratospheric distributions and global budgets of the five most abundant isotopic analogues of N₂O: ¹⁴N¹⁴N¹⁶O, ¹⁴N¹⁵N¹⁶O, ¹⁵N¹⁴N¹⁶O, ¹⁴N¹⁴N¹⁸O, and ¹⁴N¹⁴N¹⁷O. Two different chemistry models are used to derive photolysis cross sections for the analogues of N₂O: (1) the zero-point energy shift model, scaled by a factor of 2 to give better agreement with recent laboratory measurements and (2) the time-dependent Hermite propagator model. Overall, the CTM predicts stratospheric enrichments that are in good agreement with most measurements, with the latter model performing slightly better. Combining the CTM-calculated stratospheric losses for each N₂O species with current estimates of tropospheric N₂O sources defines a budget of flux-weighted enrichment factors for each. These N₂O budgets are not in balance, and trends of −0.04 to −0.06 ‰/yr for the mean of ¹⁴N¹⁵N¹⁶O and ¹⁵N¹⁴N¹⁶O and −0.01 to −0.02 ‰/yr for ¹⁴N¹⁴N¹⁸O are predicted, although each has large uncertainties associated with the sources. The CTM also predicts that ¹⁴N¹⁴N¹⁷O and ¹⁴N¹⁴N¹⁸O will be fractionated by photolysis in a manner that produces a nonzero mass-independent anomaly. This effect can account for up to half of the observed anomaly in the stratosphere without invoking chemical sources. In addition, a simple one-dimensional model is used to investigate a number of chemical scenarios for the mass-independent composition of stratospheric N₂O.

We employed a time series design to evaluate the impact of the 1989 California cigarette tax increase on cigarette consumption in California. Adult per capita consumption data from 1980 to 1990 were analyzed for California and the United States. Trend data indicated a sharp drop in California cigarette consumption coincident with the tax increase. Time-series regression analyses support this observation, and suggest that a 5% to 7% decline in consumption is attributable to the tax increase.