FC Barcelona closed 2019 as leader of LaLiga, although there's still one game of the first round to be played. That will be on Saturday, January 4 at Espanyol, at the conclusion of which the winter champion will be known. Even so, Barça are the team that have led the table for the most matches throughout the calendar year.
In 31 of the 39 match days played (79.4%), Ernesto Valverde's team have been at the top of the standings. Atlético Madrid stand out as second in the table, as they've been there for a total of 20 match days.
In the last 10 years, Barça have been the leader at the end of the calendar year eight times. Of these eight, the Catalans have ended up becoming league champions on seven of those occasions. Statistically therefore, when Barça finish the year on top of the table, it's usually a prelude to winning the domestic title.