A causal framework for evaluating drivers of policy effect heterogeneity using difference-in-differences

Sugar-sweetened beverage (SSB) taxes are promoted as key policies to reduce cardiometabolic diseases and other conditions, but comprehensive analyses of SSB taxes in the US have been difficult because of the absence of sufficiently large data samples and methods limitations. To estimate changes in SSB prices and purchases following SSB taxes in 5 large US cities. In this cross-sectional study with an augmented synthetic control analysis, changes in prices and purchases of SSBs were estimated following SSB tax implementation in Boulder, Colorado; Philadelphia, Pennsylvania; Oakland, California; Seattle, Washington; and San Francisco, California. Changes in SSB prices (in US dollars) and purchases (volume in ounces) in these cities in the 2 years following tax implementation were estimated and compared with control groups constructed from other cities. Changes in adjacent, untaxed areas were assessed to detect any increase in cross-border purchases. Data used for this analysis spanned from January 1, 2012, to February 29, 2020, and were analyzed between June 1, 2022, and September 29, 2023. The main outcomes were the changes in SSB prices and volume purchased. Using nutritional information, 5500 unique universal product codes were classified as SSBs, according to tax designations. The sample included 26 338 stores-496 located in treated localities, 1340 in bordering localities, and 24 502 in the donor pool. Prices of SSBs increased by an average of 33.1% (95% CI, 14.0% to 52.2%; P < .001) during the 2 years following tax implementation, corresponding to an average price increase of 1.3¢ per oz and a 92% tax pass-through rate from distributors to consumers. SSB purchases declined in total volume by an average of 33.0% (95% CI, -2.2% to -63.8%; P = .04) following tax implementation, corresponding to a -1.00 price elasticity of demand. The observed price increase and corresponding volume decrease immediately followed tax implementation, and both outcomes were sustained in the months thereafter. No evidence of increased cross-border purchases following tax implementation was found. In this cross-sectional study, SSB taxes led to substantial, consistent declines in SSB purchases across 5 taxed cities following price increases associated with those taxes. Scaling SSB taxes nationally could yield substantial public health benefits.

BackgroundOn October 1, 2014, the Chilean government modified its previous sugar-sweetened beverage (SSB) tax, increasing the tax rate from 13% to 18% on industrialized beverages with high levels of sugar (H-SSBs) (greater than 6.25 grams [g] sugar/100 milliliters [mL]) and decreasing the tax rate from 13% to 10% on industrialized beverages with low or no sugar (L-SSBs) (less than 6.25 g sugar/100 mL). This study examines changes in beverage prices and household beverage purchases following the implementation of the tax reform.Methods and findingsWe used longitudinal data collected between January 1, 2013, and December 31, 2015, from 2,000 households. We defined the pretax period as January 1, 2013, to September 30, 2014, and the posttax period as October 1, 2014, to December 31, 2015. We conducted a pre–post analysis for changes in prices and purchases, with the latter examined by volume and calories. We compared posttax changes in prices and purchases to a counterfactual, defined as what would have been expected in the posttax period based on pretax trends. All results are stated as comparisons to this counterfactual. We linked beverages at the bar code level to nutrition facts panel data collected by a team of Chilean nutritionists who categorized them by taxation level and beverage subcategory, which included carbonated and noncarbonated H-SSBs and concentrated, ready-to-drink L-SSBs and untaxed beverages. We reconstituted concentrated beverages and analyzed all beverages using as-consumed volumes and calories. Posttax monthly prices of H-SSBs increased, but these changes were small. Prices of carbonated H-SSBs increased by 2.0% (95% confidence interval [CI] 1.0%–3.0%), while those of noncarbonated H-SSBs increased by 3.9% (95% CI 1.6%–6.2%). Prices of L-SSB concentrates decreased after the tax by 6.7% (95% CI −8.2%–−4.6%), and prices of ready-to-drink L-SSBs increased by 1.5% (95% CI 0.3%–2.7%). Households decreased monthly per capita purchases of H-SSBs by 3.4% by volume (95% CI −5.9%–−0.9%) and 4.0% by calories (95% CI −6.3%–−1.9%), and this change was greater among high socioeconomic status (SES) households. The volume of household purchases of L-SSBs increased 10.7% (95% CI 7.5%–13.9%), while that of untaxed beverage purchases decreased by 3.1% (95% CI −5.1%–−1.1%). The main limitation of this study was that there was no control group, so we were unable to assess the causal impact of the tax.ConclusionsThe modifications of Chile’s SSB tax were small, and observed changes in prices and purchases of beverages after the tax were also small. Our results are consistent with previous evidence indicating that small increases in SSB taxes are unlikely to promote large enough changes in SSB purchases to reduce obesity and noncommunicable diseases (NCDs).

We simulate competitive benchmark wholesale prices for electricity in California during the summer of 2000, taking account of changes in gas prices, demand, and imports during this time period. We also examine the impact of changes in the prices of NOx emissions permits on the competitive benchmark prices for electricity. The competitive benchmark prices are compared to actual prices. A significant fraction of the changes in wholesale electricity prices in California during Summer 2000 can be explained by these four factors. The impact of higher NOx permit prices, and their interaction with reduced imports into California, have a particularly large impact on competitive benchmark prices. However, during June, July and August a large unexplained difference between actual prices and competitive benchmark prices remains. We attribute this difference to supplier market power and related market imperfections. We then examine whether there is evidence of strategic behavior by suppliers during the highest priced hours during the summer. Evidence of supply withholding during these hours is identified.

Not accounting for spatial heterogeneity in ecological analyses can cause modeled relationships to vary across spatial scales, specifically different levels of spatial resolution. These varying results hinder both the utility of data collected at one spatial scale for analyses at others and the determination of underlying processes. To briefly review existing methods for analyzing data collected at multiple scales, highlight the effects of spatial heterogeneity on the utility of these methods, and to illustrate a practical statistical method to account for the sources of spatial heterogeneity when they are unknown. Using simulated examples, we show how not accounting for the drivers of spatial heterogeneity in statistical models can cause contradictory findings regarding relationship direction across spatial scales. We then show how mixed effects models can remedy this multiscaling issue. Ignoring sources of spatial heterogeneity in statistical models with coarse spatial scales produced contradictory results to the true underlying relationship. Treating drivers of spatial heterogeneity as random effects in a mixed effects model, however, allowed us to uncover this true relationship. Mixed effects models is advantageous as it is not always necessary to know the influential explanatory variables that cause spatial heterogeneity and no additional data are required. Furthermore, this approach is well documented, can be applied to data having various distribution types, and is easily executable using multiple statistical packages.

BackgroundWhile food pricing is a promising strategy to improve diet, the prospective impact of food pricing on diet has not been systematically quantified.ObjectiveTo quantify the prospective effect of changes in food prices on dietary consumption.DesignWe systematically searched online databases for interventional or prospective observational studies of price change and diet; we also searched for studies evaluating adiposity as a secondary outcome. Studies were excluded if price data were collected before 1990. Data were extracted independently and in duplicate. Findings were pooled using DerSimonian-Laird's random effects model. Pre-specified sources of heterogeneity were analyzed using meta-regression; and potential for publication bias, by funnel plots, Begg's and Egger's tests.ResultsFrom 3,163 identified abstracts, 23 interventional studies and 7 prospective cohorts with 37 intervention arms met inclusion criteria. In pooled analyses, a 10% decrease in price (i.e., subsidy) increased consumption of healthful foods by 12% (95%CI = 10–15%; N = 22 studies/intervention arms) whereas a 10% increase price (i.e. tax) decreased consumption of unhealthful foods by 6% (95%CI = 4–8%; N = 15). By food group, subsidies increased intake of fruits and vegetables by 14% (95%CI = 11–17%; N = 9); and other healthful foods, by 16% (95%CI = 10–23%; N = 10); without significant effects on more healthful beverages (-3%; 95%CI = -16-11%; N = 3). Each 10% price increase reduced sugar-sweetened beverage intake by 7% (95%CI = 3–10%; N = 5); fast foods, by 3% (95%CI = 1–5%; N = 3); and other unhealthful foods, by 9% (95%CI = 6–12%; N = 3). Changes in price of fruits and vegetables reduced body mass index (-0.04 kg/m2 per 10% price decrease, 95%CI = -0.08–0 kg/m2; N = 4); price changes for sugar-sweetened beverages or fast foods did not significantly alter body mass index, based on 4 studies. Meta-regression identified direction of price change (tax vs. subsidy), number of intervention components, intervention duration, and study quality score as significant sources of heterogeneity (P-heterogeneity<0.05 each). Evidence for publication bias was not observed.ConclusionsThese prospective results, largely from interventional studies, support efficacy of subsidies to increase consumption of healthful foods; and taxation to reduce intake of unhealthful beverages and foods. Use of subsidies and combined multicomponent interventions appear most effective.

INTRODUCTION In an effort to reduce inpatient complications, the Centers for Medicare and Medicaid Services (CMS) discontinued reimbursements for certain complications beginning in October 2008. These were termed hospital-acquired conditions (HACs), and include surgical site infection, deep venous thrombosis, catheter-associated urinary tract infections, and falls, among others. The effect of this policy has not been extensively studied in the spine surgery population. METHODS A retrospective administrative insurance claims database containing data on Medicare and commercially insured patients was used to extract information on admissions associated with 1- and 2-level anterior discectomy and fusion (ACDF), lumbar laminectomy (LL), lumbar discectomy (LD), and 2- and 3-level posterior lumbar fusion (PLF). Relevant HACs were selected using International Classification of Diseases-9 codes, and a present-on-admission indicator was estimated using prior records. Difference-in-difference (DID) regressions were used to estimate the effect of the CMS nonreimbursement policy on Medicare insured patients compared to a similarly aged nonMedicare patient populations. RESULTS A total of 23 120 and 38 290 commercially insured patients met criteria. Of those, 20 265 (33%) underwent ACDF, 24 918 (41%) underwent LL or LD, and 16 227 (26%) underwent PLF. From 2007 to 2014, 2.4% (95% CI: 2.2-2.6%) and 2.2% (2.1-2.4%) of admissions were associated with at least 1 HAC in the Medicare and commercial cohorts, respectively (P = .08). A DID regression on the occurrence of any HAC, which included patients from 2007 to 2010, explained 0.8% of the total variance (adjusted multiple R2 = 0.008). Medicare insurance, postpolicy admissions, and their interaction term were not significant (all P &gt; .29). CONCLUSION In this study, we found no effect of the CMS policy on rates of HAC in spinal surgery patients. This suggests that this policy, implemented in 2008, has not reduced HAC occurrence in this spine surgery population compared to our control population.

9023 Background: Intratumor heterogeneity has been characterized among multiple cancer types. In lung adenocarcinoma, APOBEC-mutagenesis has been shown to be a source of heterogeneity. However, these data are largely limited to early stage primary tumors. There is limited information about the role of APOBEC-mutagenesis and somatic variants, copy number changes, transcript and protein expression in influencing tumor heterogeneity in metastatic lung adenocarcinoma and other thoracic tumors. Methods: We applied whole exome sequencing, RNA-seq, OncoScan CNV and mass spectrometry-based proteomic analyses on 46 tumor regions from metastatic sites including lung, liver and kidney, obtained by rapid/warm autopsy from 4 patients (pts) with stage IV lung adenocarcinoma, 1 pt each with pleural mesothelioma and thymic carcinoma. The autopsy procedure was initiated between 2-4 hours of death. Results: All tumors displayed organ-specific, branched evolution that was consistent across exome, transcriptome and proteomic analyses. The degree of heterogeneity at the genomic and proteomic level was patient-specific. There was extensive heterogeneity within the tumors of one of four patients with lung adenocarcinoma and in the thymic carcinoma patient (both non-smokers) with multiple driver mutations and copy number changes occurring in only some of the tumors suggesting ongoing late tumor evolution. Further examination of the heterogenous thymic and lung adenocarcinoma tumors showed strong enrichment with the APOBEC-mutagenesis pattern and high associated levels of APOBEC3B mRNA. Conclusions: Metastatic lung adenocarcinoma, thymic carcinoma and mesothelioma evolve through a branched, organ-specific process with marked differences in the acquisition of significant driver mutations and copy number changes. APOBEC3B is a potential driver of heterogeneity in pts with advanced, heterogeneous metastatic lung adenocarcinoma and thymic carcinoma and needs to be evaluated further.

Are Sugar-Sweetened Beverage Taxes a Cost-Effective Means of Reducing Weight?

Modeling the price competitiveness of Indonesian crops

The impact of the Oakland sugar-sweetened beverage tax on bottled soda and fountain drink prices in fast-food restaurants.

Do sugar taxes work?

The relationship between a sweetened beverage tax and changes in the prices and purchases of beverages and high-sugar food is understudied in the long term and in small independent food retail stores where sugar-sweetened beverages are among the most commonly purchased items. To examine whether a 1.5 cent-per-fluid-ounce excise tax on sugar- and artificially sweetened beverages Philadelphia, Pennsylvania, was associated with sustained changes in beverage prices and purchases, as well as calories purchased from beverages and high-sugar foods, over 2 years at small independent stores. This cross-sectional study used a difference-in-differences approach to compare changes in beverage prices and purchases of beverages and high-sugar foods (candy, sweet snacks) at independent stores in Philadelphia and Baltimore, Maryland (a nontaxed control) before and 2 years after tax implementation, which occurred on January 1, 2017. Price comparisons were also made to independent stores in Philadelphia's neighboring counties. Changes in mean price (measured in cents per fluid ounce) of taxed and nontaxed beverages, mean fluid ounces purchased of taxed and nontaxed beverages, and mean total calories purchased from beverages and high-sugar foods. Compared with Baltimore independent stores, taxed beverage prices in Philadelphia increased 2.06 cents per fluid ounce (95% CI, 1.75 to 2.38 cents per fluid ounce; P < .001), with 137% of the tax passed through to prices 2 years after tax implementation, while nontaxed beverage prices had no statistically significant change. A total of 116 independent stores and 4738 customer purchases (1950 [41.2%] women; 4351 [91.8%] age 18 years or older; 1006 [21.2%] White customers, 3185 [67.2%] Black customers) at independent stores were assessed for price and purchase comparisons. Purchases of taxed beverages declined by 6.1 fl oz (95% CI, -9.9 to -2.4 fl oz; P < .001), corresponding to a 42% decline in Philadelphia compared with Baltimore; there were no significant changes in purchases of nontaxed beverages. Although there was no significant moderation by neighborhood income or customer education level, exploratory stratified analyses revealed that declines in taxed beverage purchases were larger among customers shopping in low-income neighborhoods (-7.1 fl oz; 95% CI, -13.0 to -1.1 fl oz; P = .001) and individuals with lower education levels (-6.9 fl oz; 95% CI, -12.5 to -1.3 fl oz; P = .001). This cross-sectional study found that a tax on sweetened beverages was associated with increases in price and decreases in purchasing. Beverage excise taxes may be an effective policy to sustainably decrease purchases of sweetened drinks and calories from sugar in independent stores, with large reductions in lower-income areas and among customers with lower levels of education.

PurposeThe purpose of this study is to examine the impact of the national public cultural service system demonstration area policy on the documentary service capacity of public libraries, the differences in the effectiveness of the policy in different regions and the policy superimposition effect between the demonstration projects and the demonstration area policy.Design/methodology/approachThe study adopts the difference-in-difference (DID) method, which approximates a natural experiment, to evaluate the impact of the policy by comparatively analyzing the changes in the documentary service capacity of public libraries of the experimental and control groups.FindingsThe study reveals that the demonstration area policy can enhance the documentary service capacity of public libraries. From the perspective of urban location, it is found that there are differences in the effectiveness of the demonstration area policy on cities in different regions. The impact on cities in the eastern region is significantly higher than that on cities in the central and western regions. From the perspective of policy superimposition, it is found the demonstration projects do not have a policy superimposition effect on the demonstration area policy.Originality/valueThe study adopts a two-way fixed-effects model for DID, in addition to traditional variables, adding the individual fixed-effect, the time fixed-effect and other control variables to reduce the estimated bias caused by the omitted variables and unobservable characteristics, as well as time trends. The findings will provide a reference for governmental decision-making.

PurposeEnvironmental regulation policy and cleaner production technology innovation are the key links to achieve sustainable economic development. This paper tests the impact of Two Control Zone (TCZ) environmental regulation policy on cleaner production technology innovation and explains the heterogeneity effect between them from the perspective of regional pollution intensity and R&D investment scale.Design/methodology/approachThis paper takes TCZ policy as an environmental regulation policy and collects the patent data related to coal desulfurization cleaner production technology innovation in prefecture-level cities from 1994 to 2002 in China. This paper also tests the relationship between TCZ environmental regulation policy and cleaner production technology innovation based on difference in difference (DID) model. Take regional R&D investment scale and pollution intensity as category variables and analyze the heterogeneity effect of TCZ environmental regulation policy on cleaner production technology innovation based on difference-in-difference-in-difference (DDD) model.FindingsTCZ environmental regulation policy effectively promotes China's cleaner production technology innovation, but it is more conducive to cleaner production technology innovation in heavy pollution areas. With the increasing of R&D investment scale, the positive effect of TCZ environmental regulation policy on cleaner production technology innovation is stronger.Research limitations/implicationsOn the basis of this study, the authors should further explore the regulatory factors of the relationship between TCZ environmental regulation policy and cleaner production technology innovation and further expand the research object, so as to make the research conclusions more practical and instructive.Originality/valueThis paper tests the impact of TCZ environmental regulation policy on cleaner production technology innovation based on the prefecture city level data and DID model, and it handles the endogenous problem caused by the missing variables and provides the accurate conclusions. Moreover, this paper examines the heterogeneity effect of TCZ environmental regulation policy on cleaner production innovation from regional R&D investment scale and pollution intensity two hands and expands the existing theoretical research.

Investigating the role of emissions trading policy to reduce emissions and improve the efficiency of industrial green innovation