California, the second most racially and ethnically diverse state in the US [1], was the first state to issue mandatory stay-at-home orders to mitigate COVID-19 community spread [2]. Despite this, as of July 31, 2021, the total number of COVID-19 attributed deaths passed 63,935 (163 per 100 k people), with substantial race/ethnic differences [3]. Officially reported COVID-19 deaths of Hispanics accounted for 46% of COVID-19 deaths, and Black and Hispanic individuals experienced the highest per capita deaths [3]. However, these numbers might not reveal the full impact of COVID-19 on mortality and race/ethnic disparities due to undercounting of COVID-19 deaths [4,5,6]. It is critical for the public health and surveillance system to have an accurate picture of the differential impact of the pandemic for targeted mitigation measures. Estimating excess deaths during the pandemic reveals the severity of COVID-19 for the public health system and for race/ethnic communities.

Although prior research quantified the number of excess deaths occurring during the pandemic compared to pre-pandemic mortality trends [6,7,8,9,10,11,12,13,14,15,16], few studies have examined excess deaths stratified by race/ethnicity [5, 11,12,13,14,15,16]. We use Seasonal Autoregressive Integrated Moving Average (SARIMA) time series modeling to analyze pre-pandemic vs. pandemic trends in mortality stratified by race/ethnicity. Thus, we estimate the counterfactual number of deaths based on historical trends in mortality for each race/ethnic group and predict the numbers of excess deaths. Finally, we compare excess deaths with officially reported deaths from COVID-19 by race/ethnicity.


Study Setting, Data, and Design

We used monthly mortality data for race/ethnicities in California to undertake time series analyses in order to estimate total all-cause excess deaths due to the pandemic. Data on monthly total all-cause recorded deaths and officially reported COVID-19 mortality data for different races/ethnicities are from the Centers for Disease Control and Prevention (CDC) [17].

Using time series model estimates, we calculated differences between forecasted monthly deaths and total all-cause recorded deaths (excluding COVID-19) from January 2020 to January 2021 to gauge excess deaths for each group.

Statistical Analysis

We employed the Seasonal Autoregressive Integrated Moving Average (SARIMA) model, which has been used to analyze excess COVID-19 deaths in prior research [6]. Historical mortality trends from 2014 to 2019 were used to find the most predictive combination of seasonal autoregressive and seasonal moving average parameters. The SARIMA model produces reliable and accurate forecasting when there are seasonality patterns within the data (see the Appendix). Seasonality, randomness, and time trend are general causes of serial correlation and non-stationarity in time series. Using non-stationary time series produces spurious results, and serial correlation alters the efficiency of estimators. This makes SARIMA a proper choice in comparison with alternative methods.

Data were divided into training (2014–2018) and testing (2019) datasets for out-sample forecasting. Afterward, the model was used to predict excess mortality from January 2020 (when the 1st COVID-19 cases in California were identified) to January 2021. These predicted deaths were compared to all-cause mortality and official COVID-19-related deaths for each race/ethnic group. We calculate the number of deaths per 100,000 population for each race/ethnic group. All analyses used Rstudio (Version 1.4.1717-R 4.0.4) and Stata SE 15.1 (College Station, TX).


The SARIMA model specification was determined based on multiple criteria (see Tables 1, 2345 and 6) and Figs. 123 and 4). Our model’s prediction shows that total all-cause deaths among race/ethnic groups were higher than expected from 2020 to 2021 (Tables 178 and 9). Recorded all-cause deaths of Hispanics (93,424) exceeded predicted deaths (63,238 (95% confidence interval (CI) 59,198–67,277)) by 30,186 excess deaths—a difference of 47.7%. 27,177 deaths of the excess deaths were COVID-19 officially reported deaths. Excluding COVID-19 deaths of Hispanics, this implies 3009 all-cause deaths, or 10% of the Hispanic excess deaths, may have occurred as a result of the pandemic (compared to historical trends) and were not recorded as COVID-19 deaths. Blacks experienced 28,993 recorded all-cause deaths, which are 4903 (20.4%) higher than predicted deaths (24,090 (95%CI 21,988–26,193)). This means that 1436 all-cause deaths (29.3% of Black excess deaths) occurred above the recorded COVID-19 deaths for Blacks. Recorded all-cause deaths of Asians (40,024) exceeded predicted deaths (32,130 (95%CI 28,884–35,383)) by 7894 (24.6%) excess deaths, resulting in 1331 all-cause deaths (16.8% of the Asian excess deaths) after we exclude recorded COVID-19 deaths of Asians. Finally, comparing the predicted deaths (174,400 (95%CI 160,946–187,853)) for White non-Hispanics with recorded all-cause deaths (196,427) reveals that there were 22,027 (12.6%) excess deaths (Table 10). Hence, there were 5194 all-cause deaths (23.6% of White non-Hispanic excess deaths) after excluding official COVID-19 deaths of White non-Hispanics. Adjusting for population size, Black individuals had the highest rate of excess deaths per 100 K people (226) followed by Hispanic (194), White non-Hispanic (153), and Asian (136). Increases in all-cause deaths (excluding COVID-19 deaths) per 100 K people were 23, 66, 19, and 36 for Asian, Black, Hispanic, and White non-Hispanic individuals, respectively (Figs. 567 and 8).

Table 1 Model results for predicted deaths, total recorded deaths, and COVID-19-related deaths stratified by race/ethnicity


SARIMA time series modeling suggests that excess deaths during the pandemic are substantial and disproportionately concentrated among minorities. Hispanic excess deaths were nearly 50% higher than the number of deaths that would be predicted based on pre-pandemic mortality trends. Adjusting for population size, Black individuals had the highest rate of excess deaths per 100 k people followed by Hispanics. Reasons for our findings on the substantial race/ethnic disparities in excess deaths are unclear but may be related to differences in socioeconomic status, differential exposure to risk factors (e.g., essential workers), and healthcare-related factors including implicit biases in medical treatment [14, 15, 18, 19, 20]. Education, occupation, income, social status, and political views may alter individuals’ decisions about infection and hospitalization risks, mask wearing and other precautions, and so on. For example, low-income individuals may postpone care seeking for mild symptoms due to uninsurance and lack of paid sick leave. In addition, early diagnosis of COVID-19, access to effective COVID-19 treatments, and presence of co-morbidities will affect outcomes from infection.

More research and targeted interventions are needed to increase understanding of the drivers of COVID-19 mortality and identify policy-modifiable solutions to address excess mortality for minorities residing in California. Specifically, considering excess deaths by other causes would produce informative findings regarding COVID-19 disparities in California because mortality from heart disease and other non-COVID-19 health conditions increased during the pandemic in the USA [11]. In fact, our results on all-cause deaths excluding COVID-19 deaths imply that Black individuals followed by White non-Hispanics had the highest per-capita rates. Further research is needed to examine these disparities in non-COVID-19-related causes of mortality.

Recent research on excess deaths suggests that officially reported COVID-19 deaths understate the overall impact of the pandemic on mortality [4,5,6]. Due to the importance of excess death racial disparities to making proper health equity policy making, it is critical to have a true picture of the pandemic effect on different races/ethnic groups at the state level. Several studies have considered racial and ethnic disparities in COVID-19 mortality [11,12,13,14,15,16]. However, to our knowledge, there have been only two prior studies on race/ethnic disparities in mortality during the COVID-19 pandemic for the state of California. One study examining the period March to August 2020 reported 2077 excess deaths of Asians, 1882 excess deaths of Blacks, and 8439 excess deaths of Hispanics [14]. The second study on Hispanics reported 10,304 excess deaths in California for this population for the period March 1 to October 3, 2020 [5]. Our study extends this prior work in two key ways. First, we include data updated through January 2021 during which COVID-19 cases substantially increased in California, particularly from November 2020. For example, in contrast to the prior studies’ estimates of excess deaths among Hispanics, we find 30,186 excess deaths for this community. Second, we utilize SARIMA, which adjusts for seasonality effects in mortality trends, as well as avoids the non-stationary problem.

There are limitations that should be acknowledged. First, our study findings may not generalize beyond California. Second, we cannot conclude that excess deaths are directly attributable to COVID-19; these deaths may include those that are indirectly related such as disrupted or delayed treatment for critical health issues or undiagnosed health problems. Third, our model uses historical trends in mortality from 2014 to 2019. Above or below average historical periods of mortality may impact the accuracy of forecasts of mortality in 2020 and 2021.


Based on monthly historical trends in all-cause mortality since 2014 and using SARIMA time series modeling, our study showed significant disparities in excess mortality among race/ethnic groups, especially among Hispanic and Black individuals, compared to officially reported COVID-19 deaths. Our findings emphasize the importance of targeted policies for minority populations, such as vaccination strategies or health and social policies, to lessen the disproportionate impact of COVID-19 and future pandemics on their communities.