Stats figures are almost impossible to quantify and analysing and creating stats on Santiago pilgrims is a bit more complex than Muslim pilgrims to Haj or Sikh pilgrims to Amritsar (which attracts over 100,000 pilgrims per week.)
There are many categories of pilgrims, and tourists to Santiago.
Not all the 180 000 walking/cycling people who arrive in Santiago are pilgrims, and not all of the
± 10 million who visit Santiago by other means are tourists.
There are millions of Catholic pilgrims who arrive by bus, plane, train or car - attend mass, make confession, visit the tomb of the saint, say a prayer for the Holy Father and earn an indulgence. These pilgrims are no different from pilgrims to Rome, Jerusalem, Lourdes etc.
There are tourists who arrive in Santiago by car, planes, bus or train to see the sights, perhaps attend a mass and then move on to other cities.
There are walking Catholic pilgrims - those who arrive at the tomb of the saint, make confession, attend mass, say a prayer for the Holy Father and earn an indulgence (and a Compostela).
There are 'other' walking pilgrims - those who arrive at the tomb of the saint, attend a pilgrims' mass and earn the Compostela but who will tell you that they are not religious pilgrims.
Not all of the 'pilgrims' on the Caminos at any given time even plan to arrive in Santiago.
The Sociology department of the Cathedral, headed by Don Juan Jose Cebrian (brother pf Don Genaro, who heads the Pilgrims' office) estimated the number of pilgrims on the Camino at any one time, and those who claim the Compostela. to be 5 to 1. He came to this conclusion by using the registration in albergues, data given when the credential is obtained, and other sources, such as the tourist information offices throughout the Camino. The vast majority of pilgrims from Spain complete the Camino in four stages, as do a great many Latin Americans who only have two weeks vacation. There are also some pilgrims who do not complete the pilgrimage due to illness, injury etc. And then there are some who do not request, or get a Compostela (like me) for one reason or another.
I remember reading somewhere that all Catholic pilgrims'who visit Santiago with the intention of earning an indulgence and who comply with the requirements, are counted and are given a little prayer card. Perhaps there are stats on those pilgrims?