151 years - 0.021 years / 151 years = ~99.98%

It was closed for 8 years!

"After Egypt closed the Suez canal at the beginning of the Six-Day War on 5 June 1967, the canal remained closed for precisely eight years, reopening on 5 June 1975." from https://en.wikipedia.org/wiki/Suez_Canal#Arab%E2%80%93Israel...

I first heard about it in RealLifeLore's "The 8-Year Long Worst Traffic Jam in History" => https://youtu.be/4DiXRCo7eBs

Yup, and during that war the trapped seamen came up with their own handmade stamps (accepted as valid postage) which are now collectibles!