ABC got its third straight Thursday sweeps win last night, but its margin of victory has gotten smaller by the week.

ABC averaged a 4.4 adults 18-49 rating and 12 share, according to Nielsen overnights, just a smidge ahead of second-place CBS at 4.3/12. ABC was flat compared with last week, while CBS was up 5 percent from a 4.1/11.

The first week of the May sweeps, ABC had an even bigger advantage, averaging a 4.8/13 to CBS’s 4.0/11. CBS’s “CSI” and “Without a Trace” are up slightly since then.

Last night also marked the season finale of NBC’s “Scrubs,” which the network did not renew but is expected to return on ABC next fall. The 8:30 p.m. show averaged a mere 2.5 rating, falling 0.1 from its “My Name is Earl” lead-in.

Meanwhile, for the night, NBC was third at 2.8/8, Fox fourth at 2.0/5, Univision fifth at 1.7/5 and CW sixth at 1.3/4.
 
CBS began the night in the lead with a 4.1 at 8 p.m. for “Survivor,” with NBC second with a 2.6 for “Earl” (2.6) and “Scrubs” (2.5). ABC was third with a 2.4 for “Ugly Betty,” Fox fourth with a 1.9 for “Are You Smarter than a 5th Grader?,” Univision fifth with a 1.8 for “Al Diablo con los Guapos” and CW sixth with a 1.5 for “Smallville.”
 
At 9 p.m. ABC took the lead with a 6.1 for “Grey’s Anatomy,” while CBS slipped to second with a 4.9 for “CSI.” NBC was third with a 3.1 average for “The Office” (3.6) and the season finale of “30 Rock” (2.6), Fox and Univision tied for fourth at 2.0, Fox for “Don’t Forget the Lyrics” and Univision for “Fuego en la Sangre,” and CW was sixth with a 1.0 for “Supernatural.”
 
ABC led again at 10 p.m. with a 4.9 for “Lost,” followed by CBS with a 3.8 for “Without a Trace.” NBC was third with a 2.9 for “ER” and Univision fourth with a 1.3 for “Amas de Casa Desperadas.”
 
Among households, CBS was first for the night with a 9.5 average overnight rating and a 16 share. ABC was second at 7.7/13, NBC and Fox tied for third at 4.4/7, CW fifth at 2.1/3 and Univision sixth at 1.9/3.