Finally some one explained why investors to watch this ratio.

“Importantly,the LIBOR-OIS spread,like the TED spread, tells investors how nervous banks about each other’s credibility.If LIBOR heads higher, widening the spread to the Fed Funds Rate, it’s a signal of shrinking liquidity and banks back off from credit transactions.”

Read this article in full. It explains the ratio and its implication.

Libor3 to OIS Spread

AND also (Edited): Thanks to Flywheel

http://https://www.investopedia.com/articles/active-trading/061114/what-ois-libor-spread-and-what-it.asp

Recently I discussed the ratio in my post:

LIBOR3 to $IRX ratio once again Warning Impending crash??