Like the court of King Caracticus, "they keep passing by". This is a video of the entry procession of the recent SSPX ordination in Germany. Apparently there are, according to the Pope's letter to the bishops of the world on the reconcilliation 500 priests of the society, there are also a number of religious houses and orders who are not directly united to the SSPX throughout the world, there are seminarians who are not attached to the SSPX who study at their seminary, presumably a number of those who were ordained priest (8) or deacon (10) are not all for the the society.
If you watch the video, like me you will be amazed at the youth and number of the young men in the procession, if you compare it to the average diocesan Chrism Mass procession in most dioceses, these men seem thirty or forty years younger. I understand that in the whole of Ireland there were no more than a dozen ordinations this year, there will have been a similar number in the UK, their average age will be older than the SSPX, there were ordinations at other SSPX seminaries, at at least one, the Seminary in Winona, 13 new priests were ordained.
From the simple perspective of numbers one can see why the the Holy See is anxious to reconcile the SSPX, there is also an important lesson that at least the bishops of Europe can learn from them about being fruitful in producing vocations, and exciting young men to think about placing Christ first, especially in what is becoming increasingly a missionary environment.