Note that in the first conjoined sentence, the time period mentioned in the first conjunct (from 1998 to 2006) subsumes the time period mentioned in the second conjunct (between 2000 and 2001).
in the second conjoined sentence, the time period mentioned in the first conjunct (between 1998 to 1999) precedes the time period mentioned in the second conjunct (between 2000 and 2001).