A sharp reduction of the population of the Congo through excess deaths occurred in the Free State period but estimates of the deaths toll vary considerably. Although the figures are estimates, it is believed that as many as ten million Congolese died during the period, roughly a fifth of the population. As the first census did not take place until 1924, it is difficult to quantify the population loss of the period and these figures have been disputed by some who, like William Rubinstein, claim that the figures cited by Adam Hochschild are speculative estimates based on little evidence.