Evaluating bias and noise induced by the U.S. Census Bureau's privacy protection methods.

The U.S. Census Bureau faces a difficult trade-off between the accuracy of Census statistics and the protection of individual information. We conduct an independent evaluation of bias and noise induced by the Bureau's two main disclosure avoidance systems: the TopDown algorithm used for the 2020 Census and the swapping algorithm implemented for the three previous Censuses. Our evaluation leverages the Noisy Measurement File (NMF) as well as two independent runs of the TopDown algorithm applied to the 2010 decennial Census. We find that the NMF contains too much noise to be directly useful without measurement error modeling, especially for Hispanic and multiracial populations. TopDown's postprocessing reduces the NMF noise and produces data whose accuracy is similar to that of swapping. While the estimated errors for both TopDown and swapping algorithms are generally no greater than other sources of Census error, they can be relatively substantial for geographies with small total populations.

Widespread partisan gerrymandering mostly cancels nationally, but reduces electoral competition.

Congressional district lines in many US states are drawn by partisan actors, raising concerns about gerrymandering. To separate the partisan effects of redistricting from the effects of other factors including geography and redistricting rules, we compare possible party compositions of the US House under the enacted plan to those under a set of alternative simulated plans that serve as a nonpartisan baseline. We find that partisan gerrymandering is widespread in the 2020 redistricting cycle, but most of the electoral bias it creates cancels at the national level, giving Republicans two additional seats on average. Geography and redistricting rules separately contribute a moderate pro-Republican bias. Finally, we find that partisan gerrymandering reduces electoral competition and makes the partisan composition of the US House less responsive to shifts in the national vote.

Simulated redistricting plans for the analysis and evaluation of redistricting in the United States.

This article introduces the 50STATESIMULATIONS, a collection of simulated congressional districting plans and underlying code developed by the Algorithm-Assisted Redistricting Methodology (ALARM) Project. The 50STATESIMULATIONS allow for the evaluation of enacted and other congressional redistricting plans in the United States. While the use of redistricting simulation algorithms has become standard in academic research and court cases, any simulation analysis requires non-trivial efforts to combine multiple data sets, identify state-specific redistricting criteria, implement complex simulation algorithms, and summarize and visualize simulation outputs. We have developed a complete workflow that facilitates this entire process of simulation-based redistricting analysis for the congressional districts of all 50 states. The resulting 50STATESIMULATIONS include ensembles of simulated 2020 congressional redistricting plans and necessary replication data. We also provide the underlying code, which serves as a template for customized analyses. All data and code are free and publicly available. This article details the design, creation, and validation of the data.

The use of differential privacy for census data and its impact on redistricting: The case of the 2020 U.S. Census.

Census statistics play a key role in public policy decisions and social science research. However, given the risk of revealing individual information, many statistical agencies are considering disclosure control methods based on differential privacy, which add noise to tabulated data. Unlike other applications of differential privacy, however, census statistics must be postprocessed after noise injection to be usable. We study the impact of the U.S. Census Bureau's latest disclosure avoidance system (DAS) on a major application of census statistics, the redrawing of electoral districts. We find that the DAS systematically undercounts the population in mixed-race and mixed-partisan precincts, yielding unpredictable racial and partisan biases. While the DAS leads to a likely violation of the "One Person, One Vote" standard as currently interpreted, it does not prevent accurate predictions of an individual's race and ethnicity. Our findings underscore the difficulty of balancing accuracy and respondent privacy in the Census.

A cost-comparison of midwife-led compared with consultant-led maternity care in Ireland (the MidU study).

OBJECTIVE: to compare the cost of maternity care between two midwife-led units, and their linked consultant-led units, following a large randomised trial in Ireland. DESIGN: ethical approval was received for this unblinded, pragmatic randomised trial (MidU) funded by the Health Service Executive (Dublin North-East, Ireland), conducted 2004-2009. A comparison of costs analysis was conducted on the outcomes from the trial. SETTING: two maternity units in Ireland, with 'alongside' midwife-led units. PARTICIPANTS: all women without risk factors for labour and birth who booked at the two maternity units before 24 weeks׳ gestation were assessed for inclusion. Consenting women (n=1653) were centrally randomised on a 2:1 ratio (1101:552) to midwife-led or consultant-led care. INTERVENTIONS: women randomised to consultant-led care received standard care. Women randomised to the midwife-led arm received midwife-led care provided by a small group of midwives in two units, situated ׳alongside׳ the consultant-led units, throughout pregnancy, birth and postnatal. MEASUREMENTS: mean difference in clinician salaries, cost of care based on managers׳ data, known costs of postnatal bed days and costs of key interventions were measured. FINDINGS: the average cost of caring for a woman allocated to the midwife-led units was €2598, compared to €2780 in the consultant-led units (average difference €182 per woman, analysed by 'intention to treat'). KEY CONCLUSIONS AND IMPLICATIONS FOR PRACTICE: care in these two midwife-led units costs less than care provided by the consultant-led units. Given the clinical findings, which showed that care provided in the midwife-led units is as safe as that in the consultant-led units and results in less intervention, more midwife-led units should be incorporated into maternity care in Ireland so that scarce resources can be used more effectively.

Leptin directly activates SF1 neurons in the VMH, and this action by leptin is required for normal body-weight homeostasis.

Leptin, an adipocyte-derived hormone, acts directly on the brain to control food intake and energy expenditure. An important question is the identity of first-order neurons initiating leptin's anti-obesity effects. A widely held view is that most, if not all, of leptin's effects are mediated by neurons located in the arcuate nucleus of the hypothalamus. However, leptin receptors (LEPRs) are expressed in other sites as well, including the ventromedial hypothalamus (VMH). The possible role of leptin acting in "nonarcuate" sites has largely been ignored. In the present study, we show that leptin depolarizes and increases the firing rate of steroidogenic factor-1 (SF1)-positive neurons in the VMH. We also show, by generating mice that lack LEPRs on SF1-positive neurons, that leptin action at this site plays an important role in reducing body weight and, of note, in resisting diet-induced obesity. These results reveal a critical role for leptin action on VMH neurons.

Divergence of melanocortin pathways in the control of food intake and energy expenditure.

Activation of melanocortin-4-receptors (MC4Rs) reduces body fat stores by decreasing food intake and increasing energy expenditure. MC4Rs are expressed in multiple CNS sites, any number of which could mediate these effects. To identify the functionally relevant sites of MC4R expression, we generated a loxP-modified, null Mc4r allele (loxTB Mc4r) that can be reactivated by Cre-recombinase. Mice homozygous for the loxTB Mc4r allele do not express MC4Rs and are markedly obese. Restoration of MC4R expression in the paraventricular hypothalamus (PVH) and a subpopulation of amygdala neurons, using Sim1-Cre transgenic mice, prevented 60% of the obesity. Of note, increased food intake, typical of Mc4r null mice, was completely rescued while reduced energy expenditure was unaffected. These findings demonstrate that MC4Rs in the PVH and/or the amygdala control food intake but that MC4Rs elsewhere control energy expenditure. Disassociation of food intake and energy expenditure reveals unexpected divergence in melanocortin pathways controlling energy balance.

The hypothalamic arcuate nucleus: a key site for mediating leptin's effects on glucose homeostasis and locomotor activity.

Leptin is required for normal energy and glucose homeostasis. The hypothalamic arcuate nucleus (ARH) has been proposed as an important site of leptin action. To assess the physiological significance of leptin signaling in the ARH, we used mice homozygous for a FLPe-reactivatable, leptin receptor null allele (Lepr(neo/neo) mice). Similar to Lepr(db/db) mice, these mice are obese, hyperglycemic, hyperinsulinemic, infertile, and hypoactive. To selectively restore leptin signaling in the ARH, we generated an adeno-associated virus expressing FLPe-recombinase, which was delivered unilaterally into the hypothalamus using stereotaxic injections. We found that unilateral restoration of leptin signaling in the ARH of Lepr(neo/neo) mice leads to a modest decrease in body weight and food intake. In contrast, unilateral reactivation markedly improved hyperinsulinemia and normalized blood glucose levels and locomotor activity. These data demonstrate that leptin signaling in the ARH is sufficient for mediating leptin's effects on glucose homeostasis and locomotor activity.

Leptin receptor signaling in POMC neurons is required for normal body weight homeostasis.

Neuroanatomical and electrophysiological studies have shown that hypothalamic POMC neurons are targets of the adipostatic hormone leptin. However, the physiological relevance of leptin signaling in these neurons has not yet been directly tested. Here, using the Cre/loxP system, we critically test the functional importance of leptin action on POMC neurons by deleting leptin receptors specifically from these cells in mice. Mice lacking leptin signaling in POMC neurons are mildly obese, hyperleptinemic, and have altered expression of hypothalamic neuropeptides. In summary, leptin receptors on POMC neurons are required but not solely responsible for leptin's regulation of body weight homeostasis.