Births and deaths are derivatives. Thus a 25% spike is basically just an adjustment to reflect smaller (~2-3%) errors in the non-census years. To put numbers to

Births and deaths are derivatives. Thus a 25% spike is basically just an adjustment to reflect smaller (~2-3%) errors in the non-census years. To put numbers to this: imagine 100 people were born every year between 1991 and 2000, inclusive. The statistics only recorded 98 people being born every year, though. We then did a census, and discovered that the number of people <10 years old in 2000 was 1000 people, thus we recorded a number of births as 118 (since we thought that 882 people had been born so far in 1991-1999), and then back down to 100 in the next year.