Three Kingdoms
Population

Year
Households
Population
Notes
Eastern Han dynasty, 156
10,679,600
56,486,856
-
Shu Han, 221
200,000
900,000
-
Shu Han, 263
280,000
1,082,000
At Shu's demise, the population contained 102,000 armed soldiers and 40,000 various officials.
Eastern Wu, 238
520,000
2,567,000
-
Eastern Wu, 280
530,000
2,535,000
At Wu's demise, the population had 32,000 officials, 230,000 soldiers, and 5,000 imperial concubines.
Cao Wei, 260
663,423
4,432,881
-
Western Jin dynasty, 280
2,495,804
16,163,863
After reuniting China, the Jin dynasty's population was greatest around this time.
From Zou Jiwan (Chinese: 鄒紀萬), Zhongguo Tongshi – Weijin Nanbeichao Shi 中國通史·魏晉南北朝史, (1992).
From Zou Jiwan (Chinese: 鄒紀萬), Zhongguo Tongshi – Weijin Nanbeichao Shi 中國通史·魏晉南北朝史, (1992).
From Zou Jiwan (Chinese: 鄒紀萬), Zhongguo Tongshi – Weijin Nanbeichao Shi 中國通史·魏晉南北朝史, (1992).
From Zou Jiwan (Chinese: 鄒紀萬), Zhongguo Tongshi – Weijin Nanbeichao Shi 中國通史·魏晉南北朝史, (1992).

Question: How did the population of the three Kingdoms during the Western Jin dynasty compare to the population during the Eastern Han dynasty?
Answer: The Three Kingdoms under the Jin in 280 showed a total of 16,163,863 individuals and 56,486,856 individuals under Han in 156.