Macroeconometrics:How to measure capital depreciation? In an econometric sense, how do macroeconomists measure capital depreciation $\delta$ in the formula $K_{t+1}=K_t(1-\delta)+I_{t+1}$.

What data would I need and what kind of regression would I run?
I tried to empirically estimate the rate of depreciation a couple of years ago. I gave up! Following a large literature on growth, I assumed a constant rate of depreciation eventually. I did not have data for all the variables needed to estimate the model. 


Take a look at Nadir and Prucha's modelling approach.
In chapter 7 of this book, the authors develop an accelerator model of investment. You may then calculate the depreciation rate using the parameter estimates of the model.