Research
Working papers
The Impact of Nurse Practitioner Autonomy on Patient Sorting and Health Outcomes (Job market paper)
States have expanded nurse practitioners’ (NPs) autonomy from physician oversight to increase access to care, but this raises concerns about health outcomes under independent practice. I study how patients sort between NPs and physicians as primary care providers when NPs gain full practice authority, using state-level changes in NP scope of practice and data from the Medical Expenditure Panel Survey. I find that when NPs can practice independently of physicians, patients with multiple chronic conditions visit NPs more than physicians, and diagnoses of common chronic diseases increase. However, self-reported health declines, and evidence suggests limited adherence to antibiotic prescribing guidelines by NPs following the policy change. These results suggest that full NP practice authority enhances utilization of care among higher-risk patients and increases detection of chronic diseases, but improvements in overall health are limited.
Presented at 2025 Association of Public Policy Analysis & Management Fall Research Conference (APPAM) poster session (scheduled), Seattle, WA; 2025 Southern Economics Association (scheduled), Tampa, FL; Economics Graduate Student Conference, St. Louis, MO
How Do U.S. Adults Who Vape Choose among Different E-cigarette Models and Cigarettes in Response to Prices and Taxes?
Revise and Resubmit at Health Economics
with Shaoying Ma, Hojin Park, Qian Yang, Lei Xu, John Bridges, and Ce Shang
States continue to impose e-cigarette (EC) taxes without clear evidence of the cross-price elasticities between multiple EC types and between ECs and cigarettes. Moreover, existing literature focused on EC sales or prevalence outcomes instead of consumption units of various EC types. We examined how EC and cigarette consumption respond to prices and taxes and estimated own-price and cross-price elasticities for multiple EC types using a nationally representative volumetric choice experiment (VCE) of US adults who vaped ECs in the past 30 days. In the VCE, participants made purchases for monthly consumption in response to changing tax and price levels in 9 choice sets, and 700 people were recruited and answered VCE questions during 2023. Each choice set includes disposables, pod devices, pod refill packs, pod starter kits, tank devices, eliquids, and cigarettes. Zero-inflated Poisson model was used to estimate price and tax impacts, as well as own- and cross-price elasticities of demand for these products. Increasing taxes and prices (e.g., minimum pricing floor) reduces EC consumption among US adults who vape, and different EC types are economic substitutes. Platform goods (e.g., tank devices and e-liquids, pod devices and refill packs) are economic complements. Increasing EC prices likely does not lead to higher cigarette consumption among the general adult EC-using population. The design of EC taxes by EC models and components may be needed given their complex economic relationships.
Presented at 2024 Tobacco Online Policy Seminar (TOPS); 2024 Annual Congress of the International Institute of Public Finance, Prague, Czech Republic; 2024 Midwest Economics Association Annual Conference, Chicago, IL
Impact of Physician Supply on Health Outcomes of Underserved Populations
This paper investigates the effect of the Health Professional Shortage Area (HPSA) designation on primary care physician supply and local health outcomes. The federal designation of HPSA offers financial incentives to physicians in these areas. Using an event-study design and data on physicians and regional mortality rates, I find that counties designated as HPSAs attract more new doctors to the regions and experience a decrease of 2.6 percentage points in drug-overdose death rates within two years of receiving the designations. This occurs through the arrival of more female and younger doctors to the regions, along with an increase in the frequency of doctor visits.
Presented at 2023 BGSU-OSU Graduate Student Conference on Population, Columbus, OH; 2024 Midwest Economics Association Annual Conference, Chicago, IL
Attention vs Choice in Incomplete Welfare Take-up: What Works for WIC?
with Bill Wang
We decompose the causes of incomplete take-up of welfare program benefits into two latent mechanisms: inattention, where households do not consider program participation, and active choice, where households consider participation but find it not worthwhile. To capture these two mechanisms, we model households’ take-up decision as a two-stage process: attention followed by choice. Our model allows covariates to influence both stages simultaneously, creating an identification challenge in quantifying covariates’ impact on either stage separately. Exploiting two institutional structures of welfare programs: full attention among current participants and the recertification process, we prove that attention and choice parameters are constructively identifiable. Applied to National Longitudinal Survey of Youth 1997 (NLSY97) data on the Special Supplemental Nutrition Program for Women, Infants, and Children (WIC), our model reveals substantial household-level heterogeneity in both attention and choice probabilities. Furthermore, counterfactual simulations predict that choice-nudging policies outperform attention-boosting policies. We test this prediction using data from a WIC pilot program in Vermont that sent choice-nudging and attention-boosting text messages to different households. Consistent with the counterfactual prediction, choice-nudging messages increased retention by eight to ten percentage points, while attention-boosting messages had statistically insignificant effects. Our results highlight the critical role of choice nudges in improving program take-up.
Presented at 2025 World Congress of the Econometric Society*; 2026 Allied Social Science Associations (ASSA)*; 2025 Southern Economics Association SEA graduate session*
*Presented by Bill Wang
Publications
Cost Comparison and Spending on Tobacco Products: Evidence From A Nationally Representative Sample of Adult E-cigarette Users
with Shaoying Ma, Qian Yang, Hojin Park, Yanyun He, John F. P. Bridges, and Ce Shang
Nicotine & Tobacco Research. 2024 Oct, doi:10.1093/ntr/ntae250
This study examines factors associated with adult vapers’ cost comparison between e-cigarettes and cigarettes (ie, which one is perceived to be more expensive) and expenditures (ie, dollars spent) on these two products. Among U.S. adult vapers, tobacco use frequency, and e-cigarette device type are closely related to cost measures; e-cigarette taxes are associated with cost comparison between e-cigarettes and cigarettes, suggesting potential financial disincentive for vaping. Policymakers may consider imposing differential taxes on e-cigarette product types due to their different costs to consumers.
The Association Between Product Attributes and Oral Nicotine Pouch Preference—Evidence From Online Stores
with Andrew Hardin, Shaoying Ma, Veronica Thai, Micah Berman, Darren Mays, Jian Chen, Electra D Paskett, Theodore L Wagener, and Ce Shang
Nicotine & Tobacco Research. 2025 July, https://doi.org/10.1093/ntr/ntaf137
Oral nicotine pouches (ONPs) have steadily gained popularity since first appearing in the US market during 2014, but research on how their features are associated with consumer preference remains limited. We examined how ONP characteristics, including prices, flavors, pouches per can, nicotine concentration, and ingredient claims, are associated with online ratings (1–5 stars), which measured consumer preferences in our analysis. Data on 1689 unique ONPs from 19 brands that received reviews were scraped from 4 online stores that shipped to the United States. We provide novel evidence on how ONP features are associated with consumer preferences, measured by online ratings. Larger product size (more pouches per can) is associated with lower consumer ratings, while mint flavor is associated with higher ratings. Brands are strongly correlated with ratings, impacting how consumers rate more expensive products. Restricting mint flavor, product size and certain brands may influence consumer preferences for ONPs and their subsequent use, which should be investigated in future research.
Where Do E-cigarette Users Buy Their E-cigarette Products? Results From a Nationally Representative Sample of Adult E-cigarette Users in the United States
with Shaoying Ma and Ce Shang
Nicotine & Tobacco Research. 2025 May, https://doi.org/10.1093/ntr/ntaf110
This study examined how e-cigarette purchasing locations are associated with tobacco use pattern and socio-demographics of e-cigarette users in the United States. Based on a nationally representative sample of adult e-cigarette users in 2023, the most popular purchasing locations reported by adult e-cigarette users were: vape shops, general purpose brick-and-mortar stores, and internet. Dual use of e-cigarettes and cigarettes was associated with higher odds of buying from tobacconists. Older and Hispanic adults were more likely to make online purchases. Compared with exclusive disposable users, exclusive tank system users were more likely to buy online or from vape shops, and exclusive rechargeable (pod/cartridge) users were less likely to buy from vape shops. One additional dollar tax per 1 mg of e-liquid volume was associated with higher odds of buying from somewhere else or foreign countries.
Features of disposable e-cigarettes and their association with pricing and consumer preference: Evidence from web data of US online stores
with Shaoying Ma, Aadeeba Kaareen, Qian Yang, Zefeng Qiu, Jian Chen, Micah Berman, Theodore Wagener, and Ce Shang
Addiction. 2025 Mar;120(3):514-523, doi: 10.1111/add.16719
This study uses detailed features of 2320 unique e-cigarette disposable products scraped from the websites of five US online vape shops. In US-based online vape shops, disposable e-cigarettes with higher volume sizes are associated with lower prices, suggesting that price discounts for disposables primarily take the form of volume discounts. Consumers appear to prefer disposable e-cigarettes with lower capacity batteries, high nicotine concentrations, no synthetic nicotine, and fruit/sweet flavours.