This past summer, while reviewing the numbers for the past several years and looking at the rate of increase, month-to-month as well as year-to-year, I came to the conclusion that the final 2018 total would likely be in the 350 - 360,000 range. This includes ONLY pilgrims who completed the 'appelido' form to receive a compostela, whether or not the compostela was awarded. It does NOT include folks who simply asked for a sello to indicate they made it to the end of the pilgrimage at Santiago, but did not seek a Compostela.
If you apply the same rate of growth to, say a final total of 350,000 for 2018, the total projection for 2019 would be 402,000. And for 2020, the number could reach 460,000. This is just a straight-line estimate of the past year's percentage rate of increase over the past year. In this case, I found it to be about 15 percent, 2018 over 2017.
For the last Holy Year, in 2010, the rate of increase from the previous year (2009) was 54 percent. Just sayin... Now, if you apply that rate of increase to the next Holy Year, 2021 over 2020, the result could be as high as 700,000 pilgrims.
I hope that fewer pilgrims than that actually show up. I shudder to think about accommodations, walking space, and the ability of the Pilgrim Office to even process that many pilgrims. Yikes!
Hope this helps the dialog.