Which month had less than one percent increase in crude oil price over the earlier month?

Increase in the price of crude oil in the given month with respect to the corresponding previous months:
In April → (4800 - 3980) x 100/3980 = 20.6%
In May → (4940 - 4800)/4800 x 100 ≈ 3%
In June → (4970 - 4940)/4970 x 100 = 0.6%
In August → (6250 - 5730)x 100/5730 = 9.07%
it is clear that in the month of May only increase in crude oil price has less than 1% i.e., 0.6 % over the earlier month.