Here is another option, don't know how it will perform or scale:

create table #a (ID int,CalYear int)

insert into #a values(1,1993)

insert into #a values(1,1994)

insert into #a values(1,1995)

insert into #a values(1,2001)

insert into #a values(1,2002)

insert into #a values(2,1995)

insert into #a values(2,1996)

insert into #a values(2,2000)

insert into #a values(2,2001)

insert into #a values(2,2002)

insert into #a values(2,2003)

go

with base1 as (

select

ID,

CalYear,

rn = CalYear - row_number() over (partition by ID order by CalYear asc)

from

#a

), base2 as (

select

ID,

CalYear,

rn,

cnt

from

base1 b1

cross apply (select cnt = count(*) from base1 b2 where b1.ID = b2.ID and b1.rn = b2.rn)ds(cnt)

)

select ID, max(cnt) as MaxCnt from base2 group by ID;

go

drop table #a;

go