Table 2.

Demographic comparison between sample population and city population of five Chinese cities (Unit 10,000 persons)

City	Sample			Population (2018)		p-value
	Category	Sample size (%)	±SD	Category	N (%)
Beijing	Total	1108.9 (100.0)	167.3	Total	2154.2 (100.0)
	Gender
	Male	555.2 (50.1)	81.7	Male	1095.6 (50.9)	0.879
	Female	553.7 (49.9)	85.7	Female	1058.6 (49.1)
	Age			Total 15+	1927.6
	18-64	1095.2 (98.8)	163.4	15-64	1686.2 (87.5)	< 0.001*
	65+	13.7 (1.2)	4.0	65+	241.4 (12.5)
Shanghai	Total	963.5 (100.0)	137.3	Total	1462.4 (100.0)^
	Gender
	Male	462.5 (48.0)	63.9	Male	724.1 (49.5)	0.761
	Female	501.0 (52.0)	73.4	Female	738.2 (50.5)
	Age			Total 18+	1285.9
	18-64	947.2 (98.3)	132.3	18-59	783.9 (61.0)	< 0.001*
	65+	16.3 (1.7)	5.1	60+	502.0 (39.0)
Chongqing	Total	286.0 (100.0)	46.1	Total	3101.8 (100.0)
	Gender
	Male	131.4 (45.9)	21.1	Male	1563.4 (50.4)	0.368
	Female	154.6 (54.1)	25.1	Female	1538.4 (49.6)
	Age			Total 15+	2572.3
	18-64	282.3 (98.7)	44.9	15-64	2135.0 (83.0)	< 0.001*
	65+	3.6 (1.3)	1.2	65+	437.4 (17.0)
Shenzhen	Total	489.8 (100.0)	66.6	Total	1302.7 (100.0)
	Gender
	Male	269.3 (55.0)	37.8	Male	707.8 (54.3)	0.893
	Female	220.5 (45.0)	28.9	Female	594.9 (45.7)
	Age			Total 18+	\
	18-64	487.4 (99.5)	66.2	18-64	\	NA
	65+	2.4 (0.5)	0.5	65+	\
Hong Kong	Total	42.8 (100.0)	6.7	Total	748.77 (100.0)
	Gender
	Male	18.6 (43.5)	2.9	Male	342.23 (45.7)	0.659
	Female	24.2 (56.5)	3.8	Female	406.54 (54.3)
	Age			Total 15+	663.89
	18-64	42.5 (99.3)	6.6	15 – 64	533.36 (80.3)	< 0.001*
	65+	0.3 (0.7)	0.1	65+	130.53 (19.7)

Chi-square test was used to measure the overall difference in proportion between the sample and 2018 population data. Population age group categories were based on the available census data per city; no age group data was found for Shenzhen. ^Age and sex breakdown were only available for the registered population in Shanghai. Census data sources: [42–44, 46, 62]

\ indicates the absence of data

* p ≤ 0.05 indicates significant difference