Besides, when was the last time oil prices were this low?

Inflation-adjusted oil prices reached an all-time low in 1998 (lower than the price in 1946)! And then just ten years later in June 2008 Oil prices were at the all-time monthly high for crude oil (above the 1979-1980 prices) in real inflation adjusted terms (although not quite on an annual basis).

Subsequently, question is, when was the last time oil was $20 a barrel? Oil Prices in the 1960s and 1970s

Global oil prices generally ranged between $2.50 and $3.00 a barrel until 1970. That's about $17 to $20 a barrel when adjusted for inflation. The United States was the world's dominant oil producer at that time. It regulated prices.

Secondly, are oil prices at an all time low?

The price of oil is at all-time low. Even if you put aside the technical factors that caused the May WTI futures contract to close at negative $37.63 per barrel, oil has never been this cheap, in real terms, since the 1973 oil crisis. By the numbers: Global oil demand averaged 99.9 million barrels a day last year.

What happens if oil prices stay low?

Lower oil prices mean less drilling and exploration activity because most of the new oil driving the economic activity is unconventional and has a higher cost per barrel than a conventional source of oil. Less activity can lead to layoffs which can hurt the local businesses that catered to these workers.