Answer based on context:

The Bears donned their 1940s throwbacks in their second game against the Green Bay Packers in an NFC North showdown, with a division title on the line for the Packers. After a scoreless first quarter, the Bears scored on Jay Cutler's 15-yard touchdown pass to Brandon Marshall. However, the Packers scored three unanswered touchdowns on Aaron Rodgers' touchdown passes to James Jones. The defending league MVP completed 23 of 36 passes for 291 yards, along with the touchdown passes. Cutler completed 12 of 21 passes for 135 yards with one touchdown, one interception and a 72.5 passer rating, and was sacked four times. After the Packers scored their first touchdown on Rodgers' touchdown pass to Jones late in the first half, Cutler's pass intended for Devin Hester was intercepted by Casey Hayward, which then became an eight-yard touchdown pass. The Packers then opened the second half when Rodgers threw another touchdown pass to Jones. Bears receiver Alshon Jeffery was later flagged for pass interference, nullifying a touchdown pass, and the Bears had to resort to Olindo Mare-substituting for Robbie Gould-kicking a 34-yard field goal. On the Bears following drive, they went three-and-out, and on the punt return, Randall Cobb threw a lateral to Jeremy Ross, who fumbled the ball. Anthony Walters then recovered the ball, but the Bears failed to capitalize on the turnover, failing to gain a yard, and the team had to resort to Mare's second 34-yard field goal. However, the Packers would hang on to defeat Chicago 21-13, clinching the NFC North. With the Bears' sixth straight loss to the Packers in the rivalry, the Bears dropped to 8-6. The ten penalties committed for 91 yards by the Bears are a season high.

How many points did Chicago lose by?
8