here's my code:

    select yr,count(*)  from movie
join casting on casting.movieid=movie.id
join actor on casting.actorid = actor.id
where actor.name = 'John Travolta'
group by yr

here's the question

 Which were the busiest years for 'John Travolta'. Show the number of movies he made for each year.

here's the table structure

movie(id, title, yr, score, votes, director)
actor(id, name)
casting(movieid, actorid, ord)

this is the output i am getting:

yr  count(*)
1976    1
1977    1
1978    1
1981    1
1994    1
etcetc

i need to get the rows for which count(*) is max

how do i do this?