**3. Research Results**

#### *3.1. Check Correlation Coefficient*

The correlation coefficient is a statistical quantity that measures the degree of correlation between two factors. If the correlation coefficient has a value in the range [−1, 0), that indicates the negative correlation between those two factors (that is, if this value increases, the other value decreases, and vice versa). If the correlation coefficient has a value in the range (0, 1], that indicates the positive correlation between the two factors (that is, the value of one factor increases, the value of the other factor also increases and vice versa)) The correlation coefficient has a value of 0, indicating that the two factors are independent of each other.


**Table 2.** Data of 10 LOs in 2017 (Statistics 2021).

**Table 3.** Data of 10 LOs in 2018 (Statistics 2021).


**Table 4.** Data of 10 LOs in 2019 (Statistics 2021).



**Table 5.** Data of 10 LOs in 2020 (Statistics 2021).

Based on the results obtained in Table 6, the values of correlation coefficients between factors are all positive (+). This result reflects that the factors used in the study have a positive relationship with each other (that is, when the input factors increase, the output factors also increase accordingly). In particular, the values of the correlation coefficients in this study are mostly greater than 0.5, showing that the factors have a strong correlation with each other [25]. This result confirms that the factors used in the study satisfy the correlation conditions to serve as a basis for research and analysis.

**Table 6.** Correlation coefficient (calculated by researcher).


## *3.2. Malmquist Productivity Index Results*

The authors use the Malmquist productivity index to assess the impact of the COVID-19 pandemic on the business situation of logistics enterprises in Vietnam in the period 2017–2020. The results are as shown in Table 7 and Figure 11 below.

Since the end of 2019, the COVID-19 pandemic has forced countries around the world to apply measures to prevent the spread of the disease. These include restricting logistics activities, including the export and import activities at borders. This has had a heavy impact on logistics activities, disrupting supply chains and international trade flows. Many businesses had to suspend operations, causing a backlog of goods in warehouses, factories, and distribution centers, and reduced volume of goods in circulation. At the same time, the storage costs of goods increased, especially goods in cold storage and fresh food. This made the cost of transportation and logistics services more expensive.


**Table 7.** Malmquist results (calculated by researcher).

**Figure 11.** Malmquist results (source: researcher).

Research results show that logistics businesses operating in the field of transportation have been heavily affected by the COVID-19 pandemic, so the business situation fluctuates sharply. Specifically, Malmquist LO1 decreased from 1.1643 in the period 2017–2018 to 0.7235 in the period 2019–2020; Malmquist LO5 decreased from 1.0256 for 2017–2018 to 0.9853 for 2019–2020; Malmquist LO9 decreased from 1.0732 for the period 2017–2018 to 0.9857 for the period 2019–2020; Malmquist LO10 decreased from 1.1240 for 2017–2018 to 0.9866 for 2019–2020. However, there are a number of logistics enterprises still operating effectively, including MalmquistLO4(2019–2020) = 1.2058; MalmquistLO6(2019–2020) = 1.1078; MalmquistLO7(2019–2020) = 1.4105; MalmquistLO8(2019–2020) = 1.1514. Basic logistics service businesses include the management of freight services, warehousing services, and logistics network design. Therefore, depending on the line of each business, the level of impact of the COVID-19 pandemic is different. According to the business profile, the above businesses all have the following main areas: bonded warehouse services, container freight station warehouses, cold storage, warehousing, loading and unloading, storage of import and export goods and services, freight forwarding, customs clearance, shipping agents and

cargo brokers. Some logistics enterprises have large warehouse systems, and a cold storage system to store fresh food and special goods.
