we can't see your returns so the exact reason is unknown. even though your wages are higher in 2019, withholding should have also increased to compensate but maybe it didn't. A lot depends on the W-4 you submitted for 2019 w/h. compare the 2018 and 19 returns. note that if wages went up 10% withholding would have to go up more because some of that income would be taxed in a higher bracket. If you itemized, in 2018 did the 2019 amount go up in proportion to your wages.
