Table 2.

Descriptive statistics of scientific documents in the research fields of COVID-19, COPD and Lung Cancer based on 420 days from April 2020 to June 6th, 2021

Variables	Arithmetic Mean	Std. Error
COVID-19, documents (Docs)	68,067.61	2,135.79
COPD, documents	3,743.23	74.32
Lung Cancer, documents	25,119,04	504.17
$\mathrm{\Delta }Docs\left(\%\right)of$ COVID-19, daily increment April 2020 to June2021	1.19	0.16
$\mathrm{\Delta }Docs\left(\%\right)of$ COPD, daily increment April 2020 to June2021	0.417	0.024
$\mathrm{\Delta }Docs\left(\%\right)of$ Lung Cancer, daily increment April 2020 to June2021	0.419	0.023
$\mathrm{\Delta }Docs\left(\%\right)of$ COVID-19, daily increment April-July 2020	3.16	0.56
$\mathrm{\Delta }Docs\left(\%\right)of$ COVID-19, daily increment August-December 2020	0.65	0.06
$\mathrm{\Delta }Docs\left(\%\right)of$ COVID-19, daily increment January-June 2021	0.38	0.04

COVID-19 = Coronavirus Disease 2019; COPD = Chronic Obstructive Pulmonary Disease