We determine the [OIII]λ5007 equivalent width (EW) distribution of
1.700<z<2.274 rest-frame UV-selected (MUV<−19) star-forming
galaxies in the GOODS North and South fields. We make use of deep HDUV
broadband photometry catalogues for selection and 3D-HST WFC3/IR grism spectra
for measurement of line properties. The [OIII]λ5007 EW distribution
allows us to measure the abundance of extreme emission line galaxies (EELGs)
within this population. We model a log-normal distribution to the
[OIII]λ5007 rest-frame equivalent widths of galaxies in our sample,
with location parameter μ=4.24±0.07 and variance parameter σ=1.33±0.06. This EW distribution has a mean [OIII]λ5007 EW of
168±1A˚. The fractions of z∼2 rest-UV-selected galaxies with
[OIII]λ5007 EWs greater than 500,750 and 1000A˚ are measured to
be 6.8−0.9+1.0%, 3.6−0.6+0.7%, and 2.2−0.4+0.5%
respectively. The EELG fractions do not vary strongly with UV luminosity in the
range (−21.6<MUV<−19.0) considered in this paper, consistent with
findings at higher redshifts. We compare our results to z∼5 and
z∼7 studies where candidate EELGs have been discovered through
Spitzer/IRAC colours, and we identify rapid evolution with redshift in the
fraction of star-forming galaxies observed in an extreme emission line phase (a
rise by a factor ∼10 between z∼2 and z∼7). This
evolution is consistent with an increased incidence of strong bursts in the
galaxy population of the reionisation era. While this population makes a
sub-dominant contribution of the ionising emissivity at z≃2, EELGs
are likely to dominate the ionising output in the reionisation era