Period	Population growth (millions)	growth factor over the period	average compound annual rate of growth	years to double
-8000 - 0 (lower estimate)	1-170	34-40	0.044%-0.046%	1 572
-8000 - 0 (upper estimate)	10-400			1 503
0-1000  (lower estimate)	170-254	1.49-0.86	0.040%-0.015%	1 724
0-1000  (upper estimate)	400-345			1 503
1000-1800  (lower estimate)	254-813	3.20-3.26	0.146%-0.148%	477
1000-1800  (upper estimate)	345-1125			469
1800-1950  (lower estimate)	813-2400	2.95-2.27	0.724%-0.549%	96
1800-1950  (upper estimate)	1125-2556			127
1950-2000	2556-6079	2.38	1.748%	40