Changes in prices, sales, consumer spending, and beverage consumption one year after a tax on sugar-sweetened beverages in Berkeley, California, US: A before-and-after study

BackgroundTaxes on sugar-sweetened beverages (SSBs) meant to improve health and raise revenue are being adopted, yet evaluation is scarce. This study examines the association of the first penny per ounce SSB excise tax in the United States, in Berkeley, California, with beverage prices, sales, store revenue/consumer spending, and usual beverage intake.Methods and findingsMethods included comparison of pre-taxation (before 1 January 2015) and first-year post-taxation (1 March 2015–29 February 2016) measures of (1) beverage prices at 26 Berkeley stores; (2) point-of-sale scanner data on 15.5 million checkouts for beverage prices, sales, and store revenue for two supermarket chains covering three Berkeley and six control non-Berkeley large supermarkets in adjacent cities; and (3) a representative telephone survey (17.4% cooperation rate) of 957 adult Berkeley residents.Key hypotheses were that (1) the tax would be passed through to the prices of taxed beverages among the chain stores in which Berkeley implemented the tax in 2015; (2) sales of taxed beverages would decline, and sales of untaxed beverages would rise, in Berkeley stores more than in comparison non-Berkeley stores; (3) consumer spending per transaction (checkout episode) would not increase in Berkeley stores; and (4) self-reported consumption of taxed beverages would decline.Main outcomes and measures included changes in inflation-adjusted prices (cents/ounce), beverage sales (ounces), consumers’ spending measured as store revenue (inflation-adjusted dollars per transaction) in two large chains, and usual beverage intake (grams/day and kilocalories/day).Tax pass-through (changes in the price after imposition of the tax) for SSBs varied in degree and timing by store type and beverage type. Pass-through was complete in large chain supermarkets (+1.07¢/oz, p = 0.001) and small chain supermarkets and chain gas stations (1.31¢/oz, p = 0.004), partial in pharmacies (+0.45¢/oz, p = 0.03), and negative in independent corner stores and independent gas stations (−0.64¢/oz, p = 0.004). Sales-unweighted mean price change from scanner data was +0.67¢/oz (p = 0.00) (sales-weighted, +0.65¢/oz, p = 0.003), with +1.09¢/oz (p 0.001) for sodas and energy drinks, but a lower change in other categories. Post-tax year 1 scanner data SSB sales (ounces/transaction) in Berkeley stores declined 9.6% (p 0.001) compared to estimates if the tax were not in place, but rose 6.9% (p 0.001) for non-Berkeley stores. Sales of untaxed beverages in Berkeley stores rose by 3.5% versus 0.5% (both p 0.001) for non-Berkeley stores. Overall beverage sales also rose across stores. In Berkeley, sales of water rose by 15.6% (p 0.001) (exceeding the decline in SSB sales in ounces); untaxed fruit, vegetable, and tea drinks, by 4.37% (p 0.001); and plain milk, by 0.63% (p = 0.01). Scanner data mean store revenue/consumer spending (dollars per transaction) fell 18¢ less in Berkeley (−$0.36, p 0.001) than in comparison stores (−$0.54, p 0.001). Baseline and post-tax Berkeley SSB sales and usual dietary intake were markedly low compared to national levels (at baseline, National Health and Nutrition Examination Survey SSB intake nationally was 131 kcal/d and in Berkeley was 45 kcal/d). Reductions in self-reported mean daily SSB intake in grams (−19.8%, p = 0.49) and in mean per capita SSB caloric intake (−13.3%, p = 0.56) from baseline to post-tax were not statistically significant.Limitations of the study include inability to establish causal links due to observational design, and the absence of health outcomes. Analysis of consumption was limited by the small effect size in relation to high standard error and Berkeley’s low baseline consumption.ConclusionsOne year following implementation of the nation’s first large SSB tax, prices of SSBs increased in many, but not all, settings, SSB sales declined, and sales of untaxed beverages (especially water) and overall study beverages rose in Berkeley; overall consumer spending per transaction in the stores studied did not rise. Price increases for SSBs in two distinct data sources, their timing, and the patterns of change in taxed and untaxed beverage sales suggest that the observed changes may be attributable to the tax. Post-tax self-reported SSB intake did not change significantly compared to baseline. Significant declines in SSB sales, even in this relatively affluent community, accompanied by revenue used for prevention suggest promise for this policy. Evaluation of taxation in jurisdictions with more typical SSB consumption, with controls, is needed to assess broader dietary and potential health impacts.

研究背景 旨在改善公众健康并增加财政收入的含糖饮料（sugar-sweetened beverages, SSBs）税政策正逐步落地，但相关评估研究仍较为匮乏。本研究针对美国加利福尼亚州伯克利市推行的全美首项每盎司征收1美分的含糖饮料消费税，考察其与饮料价格、销量、门店营收与消费者支出，以及居民常规饮料摄入量之间的关联。
研究方法与结果 本研究的分析时段分为税前（2015年1月1日前）与税后首年（2015年3月1日至2016年2月29日），评估内容包含三部分：①伯克利市26家门店的饮料价格；②覆盖伯克利市3家及周边非伯克利市6家大型超市的两大连锁商超的1550万笔结账销售点扫描数据，用于分析饮料价格、销量与门店营收；③针对957名伯克利成年居民的代表性电话调查（合作率17.4%）。
本研究的核心研究假设包括：①2015年伯克利市开征此项税后，相关连锁门店的应税饮料售价将完全转嫁税负；②与非伯克利市的对照门店相比，伯克利门店的含糖饮料销量将出现下滑，而非应税饮料销量则会上升；③伯克利门店的每笔结账交易的消费者支出不会增加；④受访者自我报告的应税饮料摄入量将有所下降。
主要结局与测量指标包括：经通胀调整后的饮料价格变化（美分/盎司）、饮料销量（盎司）、以门店营收（经通胀调整后的每笔交易美元金额）衡量的消费者支出，以及居民常规饮料摄入量（克/天与千卡/天）。
含糖饮料的税负转嫁（即征税后价格的变化幅度）程度与时机因门店类型与饮料品类而异。大型连锁超市实现完全税负转嫁（每盎司上涨1.07美分，p=0.001），小型连锁超市与连锁加油站亦实现完全转嫁（每盎司上涨1.31美分，p=0.004），药房仅实现部分转嫁（每盎司上涨0.45美分，p=0.03），而独立便利店与独立加油站则出现负转嫁（每盎司下降0.64美分，p=0.004）。销售点扫描数据显示，未按销量加权的平均价格变化为每盎司+0.67美分（p=0.00）；按销量加权后为每盎司+0.65美分（p=0.003），其中碳酸饮料与能量饮料的价格涨幅达每盎司+1.09美分（p<0.001），其余品类涨幅相对较低。
税后首年的销售点扫描数据显示，伯克利门店的含糖饮料销量（每笔交易盎司数）较未征税情境下的预估水平下降9.6%（p<0.001），而非伯克利市对照门店的含糖饮料销量则上升6.9%（p<0.001）。伯克利门店的非含糖饮料销量上升3.5%，而非伯克利市对照门店仅上升0.5%（两者p均<0.001）。所有门店的整体饮料销量均有所上升。在伯克利门店中，饮用水销量增幅达15.6%（p<0.001，其增幅超过了含糖饮料的销量降幅），非含糖的果汁、蔬菜饮料与茶饮增幅达4.37%（p<0.001），纯牛奶增幅达0.63%（p=0.01）。销售点扫描数据显示，伯克利门店的平均门店营收/消费者支出（每笔交易美元金额）较对照门店（每笔交易下降0.54美元，p<0.001）仅少下降18美分（每笔交易下降0.36美元，p<0.001）。
伯克利市的基线含糖饮料销量与常规饮食摄入量显著低于全国平均水平（基线时，全国健康与营养调查（National Health and Nutrition Examination Survey, NHANES）显示全国人均含糖饮料日摄入量为131千卡/天，伯克利市仅为45千卡/天）。从基线至税后时段，受访者自我报告的含糖饮料日摄入量均值（克）下降19.8%（p=0.49），人均含糖饮料日热量摄入均值下降13.3%（p=0.56），但上述变化均无统计学显著性。
本研究存在一定局限性：由于采用观察性研究设计，无法确立因果关联；且未纳入健康结局指标。由于标准误较高且伯克利市基线摄入量较低，摄入量分析的效应量较小，进一步限制了研究结论的推广性。
研究结论：在全美首项大型含糖饮料税实施一年后，尽管并非所有场景下的含糖饮料价格均出现上涨，但伯克利市的含糖饮料销量有所下滑，非含糖饮料（尤其是饮用水）与本次研究覆盖的整体饮料销量均出现上升；本次研究门店的每笔交易消费者总支出并未增加。两类独立数据源均显示含糖饮料价格上涨，且上涨时机与应税、非应税饮料的销量变化模式均提示，观测到的变化可归因于该项税收政策。税后自我报告的含糖饮料摄入量与基线相比无显著变化。即便在这个相对富裕的社区，含糖饮料销量的显著下降（伴随税收收入用于公共健康预防项目）也提示该项政策具备应用前景。未来需在含糖饮料摄入量更具代表性的地区开展带对照的税收评估，以考察其对饮食与潜在健康影响的更广泛效应。