"has been going downwards for 15 consecutive years" that was the claim. It's not been going down for 15 consecutive years as there has been ups and downs during the past 15 years. The overall trend is down, but going downwards for 15 years in a row is not true.
You ignored the "15 consecutive years".
Not that it matters much, but it went from 5.52 to 5.55 to 5.46 to 5.55 and then down to 5.29 since 2016. It was a bit of a pedantic point but it's 6 consecutive years.