Under what condition will unemployment rate decrease despite the number of unemployed people increases?

Recall that Labour force = unemployed person + employed person.

If the number of unemloyed person increases, labour force also increases. Therefore, the change in unemployment rate can increase, decrease or do not change, depending on the magnitude of increase of unemployed person and labour force.

If the percentage increase in unemployed person is smaller than the percentage increase in labour force, then the unemployment rate will decrease.