zIndex not working

Dash Python
1

Hi, I can’t seem to put my dropdowns and radioitems at the top of the page when using zIndex. Am I doing it correctly? thank you

import dash
import dash_bootstrap_components as dbc
import dash_html_components as html



app.layout = \
dbc.Container([html.H4('Report '), style ={'text-align': 'center'}), html.Hr(),
          dbc.Row([dbc.Col(html.Div(children = [html.Label(['Top Diff:'], style = {'font-weight':'bold'}), #'margin-left':'8px'
                                               dcc.Dropdown(id='dropdown_diff'])],
                                    style = {'zIndex':9999999999}), sm=3),
                  dbc.Col(html.Div(children = [html.Label(['Industries: '], style = {'font-weight':'bold','text-align':'center'}),
                                               dcc.Dropdown(id = 'dd_industries', multi = True)],
                                   style = {'zIndex':9999999999}), sm=3),
                  dbc.Col(html.Div(children = [html.Label(['Countries: '], style = {'font-weight':'bold','text-align':'center'}),
                                               dcc.Dropdown(id = 'dd_countries', multi = True)],
                                   style = {'zIndex':9999999999}), sm=3),
                  dbc.Col(html.Div(children = [html.Label(['Ratings: '], style = {'font-weight':'bold','text-align':'center'}),
                                               dcc.Dropdown(id = 'dd_ratings', options = option_ratings, value = [], multi = True)],
                                   style = {'zIndex':9999999999}), sm=3)    ])])

if __name__ == '__main__':
    app.run_server()