Make bars in animated bar graph increase at same speed

If you are asking for all seven bars to arrive at their destination at the same time all you have to do is set the ending keyframes at the same point in the timeline.

If you are asking for all bars to move something like 7 pixels per second and stop at the appropriate place you'll have to add a rather complex expression to the slider that controls the height of each bar. I don't have time to write it for you but what I would do is add a marker or set one keyframe with the starting value to the layer where you want the movement to start, combine the marker time in an if statement with this kind of logic:

if (time < marker time or keyframe time) take the current value of the slider or else add the time past the marker to the slider value until you get to the final value.

That is the basic logic you would follow. I don't have time to open AE and test it so I'm not going to give you any code to try.

If the speed just has to be close then open up the Graph Editor, drag the last keyframe out until you get the speed you like, make a note of the speed graph value, then move to each animated property and adjust the distance between keyframes until you get something very close to the same value. If the animated bar chart isn't going to be changed every a bunch of times I'd probably just use the graph editor instead of writing an expression following the logic I wrote above in italics. The graph editor should be able to get you very close to the same speed for each bar, but they will all have to start or end at different times.

EDIT: I wrapped up my current project early so here's what I came up with for an expression to control the speed of the slider:

kt = key(1).time;

st = time - kt;

rte = .5 // edit this to change speed

sf = st / thisComp.frameDuration;

inc = value + sf * rte;

fv = 50; // edit this to change the final value

if (st < 0) value

  else inc

if (inc > fv) fv

The first line (kt =) returns the time of the first keyframe for the slider. The second line (st =) sets the start time of a counter to zero at the first keyframe. Any frame before is a negative number, any frame after is a positive number. The third line (rte =) sets the rate of the increase to .5 per frame. The fourth line (sf =) converts time to frames to give me easier numbers to work with. The fifth line (inc =) adds the increase times the rate to the current value of the slider. The sixth line (fv =) defines the final value for the slider as 50.

The if statement says if the start time is less then zero then do nothing. When the start time is greater than zero increase the value. The last if argument simply says when the increased value is greater than the final value keeps the final value.

This expression will start the slider at the first keyframe and then increase the value by .5 every frame until it gets to the final value of 50.

If you wanted to ease in and out it would take about 6 more lines of code. Personally, I think that using the graph editor to set up the animations on only 7 layers would be much easier. Here's what two different sets of keyframes between different values look like when they have an ease in and out and the same average speed:

The speed is very close but the time to get there is different. All I did was drag the end keyframe out a bit to get approximately the same speed for both animations. It took about 2 seconds.