Consider a class of long-run variance estimators
$$
\hat{J_T}\equiv\hat{\gamma}_0+2\sum_{j=1}^{T-1}k\left(\frac{j}{\ell_T}\right)\hat{\gamma}_j
$$
$k$ is a kernel or weighting function, the $\hat\gamma_j$ are sample autocovariances. $k$, among other things must be symmetric and have $k(0)=1$. $\ell_T$ is a bandwidth parameter.
Newey & West (Econometrica 1987) propose the Bartlett kernel
$$k\left(\frac{j}{\ell_T}\right) = \begin{cases}
\bigl(1 - \frac{j}{\ell_T}\bigr)
\qquad &\mbox{for} \qquad 0 \leqslant j \leqslant \ell_T-1 \\
0 &\mbox{for} \qquad j > \ell_T-1
\end{cases}
$$
Hansen & Hodrick's (Journal of Political Economy 1980) estimator amounts to taking a truncated kernal, i.e., $k=1$ for $j\leq M$ for some $M$, and $k=0$ otherwise. This estimator is, as discussed by Newey & West, consistent, but not guaranteed to be positive semi-definite (when estimating matrices), while Newey & West's kernel estimator is.
Try $M=1$ for an MA(1)-process with a strongly negative coefficient $\theta$. The population quantity is known to be $J = \sigma^2(1 + \theta)^2>0$, but the Hansen-Hodrick estimator may not be:
set.seed(2)
y <- arima.sim(model = list(ma = -0.95), n = 10)
acf.MA1 <- acf(y, type = "covariance", plot = FALSE)$acf
acf.MA1[1] + 2 * acf.MA1[2]
## [1] -0.4056092
which is not a convincing estimate for a long-run variance.
This would be avoided with the Newey-West estimator:
acf.MA1[1] + acf.MA1[2]
## [1] 0.8634806
Using the sandwich
package this can also be computed as:
library("sandwich")
m <- lm(y ~ 1)
kernHAC(m, kernel = "Bartlett", bw = 2,
prewhite = FALSE, adjust = FALSE, sandwich = FALSE)
## (Intercept)
## (Intercept) 0.8634806
And the Hansen-Hodrick estimate can be obtained as:
kernHAC(m, kernel = "Truncated", bw = 1,
prewhite = FALSE, adjust = FALSE, sandwich = FALSE)
## (Intercept)
## (Intercept) -0.4056092
See also NeweyWest()
and lrvar()
from sandwich
for convenience interfaces to obtain Newey-West estimators of linear models and long-run variances of time series, respectively.
Andrews (Econometrica 1991) provides an analysis under more general conditions.
As to your subquestion regarding overlapping data, I would not be aware of a subject-matter reason. I suspect tradition is at the roots of this common practice.