Okay, I've done the research... Below shows the perecentage of the total point tally to win the league at the halfway point of the season.

Red, you are thinking about 2002 I guess.

If you average it out over these 25 years, it comes out at exactly 50% at the halfway point

2000 Man Utd 47%
2001 Man Utd 54%
2002 Arsenal 41%
2003 Man Utd 47%
2004 Arsenal 50%
2005 Chelsea 48%
2006 Chelsea 57%
2007 Man Utd 53%
2008 Man Utd 52%
2009 Man Utd 46%
2010 Chelsea 49%
2011 Man Utd 51%
2012 Man City 51%
2013 Man Utd 52%
2014 Man City 48%
2015 Chelsea 53%
2016 Leicester 48%
2017 Chelsea 53%
2018 Man City 55%
2019 Man City 45%
2020 Liverpool 56%
2021 Man City 48%
2022 Man City 51%
2023 Man City 47%
2024 Man City 44%
2025 Liverpool 55%