  The lithium doublet at 6708 \AA\ provides an age diagnostic for main sequence
FGK dwarfs. We measured the abundance of lithium in 1305 stars with detected
transiting planets from the Kepler Mission using high-resolution spectroscopy.
Our catalog of lithium measurements from this sample have a range of abundance
from A(Li) = 3.11 $\pm$ 0.07 to an upper limit of $-$0.84 dex. For a
magnitude-limited sample that comprises 960 of the 1305 stars, our Keck-HIRES
spectra have a median S/N = 45 per pixel at $\sim$6700 \AA\ with spectral
resolution $\frac{\lambda}{\Delta \lambda}$ = $R$ = 55,000. We identify 80
young stars that have A(Li) values greater than the Hyades at their respective
effective temperatures; these stars are younger than $\sim$650 Myr old, the
approximate age of the Hyades. We then compare the distribution of A(Li) with
planet size, multiplicity, orbital period, and insolation flux. We find larger
planets preferentially in younger systems, with an A-D two-sided test p-value =
0.002, a $>3\sigma$ confidence that the older and younger planet samples do not
come from the same parent distribution. This is consistent with planet
inflation/photoevaporation at early ages. The other planet parameters ($Kepler$
planet multiplicity, orbital period, and insolation flux) are uncorrelated with
age.
