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The most positive opening bid is 2NT and 1NT. One very interesting point. Although they are the most positive opening, but if the final contract is 2NT, it is negative. So 2NT as a contract is really not a good % play. In fact there are no other positive contracts other then the usual 8, namely 1H 1S 1NT 2H 2S 3NT, 4H and 4S.

1NT opening:-

********** Total
NS each level one line from 1 to 7; C D H S NT ave IMP , ave MP;(total for level)
-1.#J -1.#J%; -1.#J -1.#J%; -1.#J -1.#J%; -1.#J -1.#J%; 0.23 54.05%; ( 0.23 54.05%)
-1.56 42.61%; -0.76 43.95%; 0.29 54.69%; 0.26 54.60%; -1.06 46.93%; (-0.19 51.26%)
-0.80 46.51%; -0.59 46.42%; -0.74 46.97%; -0.68 47.38%; 0.53 53.26%; ( 0.34 52.29%)
-1.12 44.83%; -1.18 43.36%; 0.20 50.63%; 0.17 50.17%; -0.93 48.37%; ( 0.13 50.16%)
-1.23 36.59%; -1.19 35.09%; -2.20 40.84%; -2.40 39.12%; -3.79 39.65%; (-1.72 37.89%)
0.28 46.70%; 0.31 45.95%; 0.15 45.71%; -0.24 47.10%; -0.24 49.76%; (-0.05 47.85%)
-0.28 43.57%; 0.07 50.80%; -1.96 41.00%; 0.18 47.86%; -0.38 53.79%; (-0.52 50.18%)
Pass imp = -1.#J mp = -1.#J%; Total imp = 0.142101 mp = 51.555972%;
EW each level one line from 1 to 7; C D H S NT ave IMP , ave MP;(total for level)
-1.#J -1.#J%; -1.#J -1.#J%; -1.#J -1.#J%; -1.#J -1.#J%; -1.#J -1.#J%; (-1.#J -1.#J%)
-0.17 48.36%; -0.34 47.83%; 0.31 54.45%; 0.28 54.37%; -1.95 41.09%; ( 0.12 52.51%)
-1.24 43.86%; -0.98 45.41%; -0.49 47.52%; -0.30 49.06%; -0.70 39.48%; (-0.72 46.35%)
-1.75 41.45%; -1.59 39.41%; -0.03 47.09%; 0.15 47.33%; -4.17 25.33%; (-0.27 45.55%)
-3.08 32.85%; -2.87 34.79%; -2.84 33.96%; -2.51 36.18%; -14.80 2.49%; (-2.91 34.03%)
-5.99 29.95%; -3.55 39.33%; -2.31 29.97%; -2.11 33.58%; -11.87 29.40%; (-3.49 33.19%)
-5.94 13.49%; -6.42 37.87%; -8.36 28.33%; -3.29 60.40%; 13.73 0.00%; (-6.22 28.59%)
Pass imp = 1.#R mp = -1.#J%; Total imp = -0.305968 mp = 49.174816%;
Combined into NS imp = 0.167227 mp = 51.450046%;

2NT opening:-

********** Total
NS each level one line from 1 to 7; C D H S NT ave IMP , ave MP;(total for level)
-1.#J -1.#J%; -1.#J -1.#J%; -1.#J -1.#J%; -1.#J -1.#J%; -1.#J -1.#J%; (-1.#J -1.#J%)
-1.#J -1.#J%; -1.#J -1.#J%; -1.#J -1.#J%; -1.#J -1.#J%; -0.63 49.14%; (-0.63 49.14%)
-2.00 46.82%; -1.00 45.57%; -0.45 49.05%; -0.75 49.57%; 0.44 53.52%; ( 0.37 53.26%)
-2.15 35.96%; -2.37 38.00%; 0.21 51.40%; 0.18 51.07%; -1.63 45.03%; ( 0.11 50.83%)
-1.68 31.05%; -1.54 32.07%; -2.77 36.85%; -2.83 37.76%; -3.43 36.55%; (-2.26 34.99%)
0.54 46.50%; 0.22 46.83%; 0.49 46.54%; 0.35 48.83%; -0.06 51.95%; ( 0.21 49.89%)
-1.31 37.03%; -0.54 42.60%; -0.92 43.30%; -0.94 46.04%; 0.57 55.23%; (-0.15 50.98%)
Pass imp = -1.#J mp = -1.#J%; Total imp = 0.126568 mp = 51.348383%;
EW each level one line from 1 to 7; C D H S NT ave IMP , ave MP;(total for level)
-1.#J -1.#J%; -1.#J -1.#J%; -1.#J -1.#J%; -1.#J -1.#J%; -1.#J -1.#J%; (-1.#J -1.#J%)
-1.#J -1.#J%; -1.#J -1.#J%; -1.#J -1.#J%; -1.#J -1.#J%; -1.#J -1.#J%; (-1.#J -1.#J%)
-1.57 35.81%; -1.68 35.51%; -1.75 40.27%; -1.64 40.48%; -0.99 35.33%; (-1.64 39.10%)
-4.68 28.99%; -3.96 25.27%; -1.69 38.08%; -1.33 39.77%; 2.64 35.73%; (-2.21 35.81%)
-3.62 28.20%; -4.14 26.97%; -3.35 30.98%; -2.86 32.35%; -4.44 0.00%; (-3.56 29.00%)
-2.24 26.74%; -4.23 25.06%; -1.40 35.90%; -2.77 28.86%; -0.98 30.22%; (-2.36 29.99%)
-5.63 23.09%; -4.08 19.45%; -1.93 37.77%; -5.59 35.67%; -1.#J -1.#J%; (-4.33 26.83%)
Pass imp = 1.#R mp = -1.#J%; Total imp = -2.129566 mp = 36.566763%;
Combined into NS imp = 0.176344 mp = 51.620434%;