yes it's slowing down, over geologic time, but it hasn't suddenly lost a second. This is an accumulated error between the rate of ratation and the official definition of the second back in about 1950.

If you look in your link at the dates when leap seconds have been added, we've actually had an extended period of NOT adding one!

12/31/1998
6/30/1997
12/31/1995
6/30/1994
6/30/1993
6/30/1992
12/31/1990
12/31/1989
12/31/1987
6/30/1985
6/30/1983
6/30/1982
6/30/1981
12/31/1979
12/31/1978
12/31/1977
12/31/1976
12/31/1975
12/31/1974
12/31/1973
12/31/1972
6/30/1972

the average is 22 seconds in 34 years. it used to be a fairly regular annual occurrence.

"And then, in 1999 for reasons still unknown, the rotation of the Earth speeded up a bit, so we haven't had to add a second since then," O'Brian told LiveScience in a telephone interview.

Interestingly, the USA's global positioning system isn't designed to accomodate leap seconds and there are fierce arguments in the timekeeping community about whether we should have taken the leap second or not.