increased (an increase)

rose (a rise)

grew (a growth)

developed (a development)

escalated (an escalation)

shot up

rocketed

went down ( a downward trend)

decreased (a decrease)

fell (a fall)

declined (a decline)

dropped (a drop)

plunged (a plunge)

tumbled (a tumble)

crashed ( a crash)

plummeted

remained almost the same (a period of almost no change)

Remained stable (stability)

Stabilized (stability)

Levelled off/ levelled out (the levelling off/out)

Reached a plateau (only used when the trend is up and then levels off)

was erratic

was volatile

fluctuated (fluctuations, unstability)