Some data points were not used because I found them only after making the graph. Also (Animal World 1972) is a poor source, as it's an encyclopedia without citations.
References:
Kemf & Phillips. 1994. Whales in the Wild. World Wildlife Fund, Gland, Switzerland.
IUCN 1966 Red Data Book. Vol. 1 - Mammalia. International Union for the Conservation of Nature and Natural Resources, Morges, Switzerland.
Oryx 1964a. Whaling agreement hitch. Oryx 7:145.
Burton & Pearson. 1987. Rare Mammals of the World. Stephen Greene Press, Lexington, MA, USA.
Nowak & Paradiso. 1983. Walker's Mammals of the World, vols. 1 and 2. 4th edition. Johns Hopkins University Press, Baltimore, MD, USA.
Klinowska, M. 1991. Dolphins, Porpoises and Whales of the World - The IUCN Red Data Book. IUCN. Gland, Switzerland.
Animal World 1972 = Encyclopedia of the Animal World, 1972. p699 (not used in graph)
Notes
Commercial exploitation of whales began in the 19th century.
Average of estimates used rather than error bars.
IUCN estimates may be only of mature individuals (need to check that).
Prewhaling population may be a huge under-estimate. A recent study (2003) gives population estimates for fin and humpback whales far greater than those previously calculated for prewhaling populations. Similar studies have not yet been done for Blue Whales. (Roman, J and S.R. Palumbi. 2003. Whales Before Whaling in the North Atlantic. Science. 301: 508-510. PDFarchive copy at the Wayback Machine)
Tools
Made in OpenOffice Calc (v2.1), exported to SVG by first copying into Draw, and then practically recreated in Inkscape (v0.45). I don't recommend this way of making a graph.