Figures from a Gallup study were used to explain the characteristics of sequential choice in Democracy with sequential choice and fund voting (chapter II.A.3, No need to hold elections in two rounds). The figures were from the presidential elections in Iceland in 1996. Certainly, the nominations of candidates were then not on the terms for sequential choice. Therefore, such figures don't bear a wider meaning for comparison.
How sequential choice influences the conditions for candidacy is shown in the article How the presidential election becomes the more trustworthy the more candidates there are.